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  • General Chemistry  (2,260)
  • Life and Medical Sciences  (949)
  • Cell & Developmental Biology  (611)
  • 1995-1999  (2,794)
  • 1945-1949  (415)
  • 1997  (2,794)
  • 1947  (327)
  • 1946  (88)
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  • 1995-1999  (2,794)
  • 1945-1949  (415)
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  • 101
    Electronic Resource
    Electronic Resource
    Dendritic Bipyridine Ligands and Their Tris(Bipyridine)Ruthenium(II) Chelates - Syntheses, Absorption Spectra, and Photophysical Properties (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 706-712 
    Details
    ISSN: 0947-6539
    Keywords: bipyridine ligands ; dendrimers ; dioxygen quenching ; luminescence ; ruthenium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several synthetic strategies have been explored to prepare dendrimers having the [Ru(bpy)3]2+ complex as their core (bpy = 2,2′-bipyridine). Dendritic ligands have been synthesized by attaching branches in the 4,4′-positions of bpy. The largest dendritic bipyridine ligand contains 54 peripherical methylester units. Four RuII dendritic complexes have been prepared. Their absorption and emission spectra are very similar to those of the unsubstituted parent RuII-bipyridine complexes. The large dendritic complexes, however, exhibit a more intense emission and a longer excited-state lifetime than [Ru(bpy)3]2+ in aerated solutions. This is due to the shielding effect of the dendrimer branches on the Ru-bipyridine core, which limits the quenching effect of molecular oxygen. For the largest dendritic complex, which contains 54 peripherical methylester units, the excited-state lifetime in aerated acetonitrile solution is longer than 1 μs, and the rate constant for dioxygen quenching is twelve times smaller than for [Ru(bpy)3]2+.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030509
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  • 102
    Electronic Resource
    Electronic Resource
    Synthesis of (R)-Sulforaphane Using [cpru(R, R)-CHIRAPHOS)]+ as Chiral AuxiliaryEnantioselective organic syntheses using chiral transition metal complexes, part 3. For part 2 see ref. [1]. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 713-716 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric synthesis ; dioxiranes ; ruthenium ; sulforaphane ; sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new enantioselective (80% ee) synthesis of (R)-sulforaphane and its epimer (S)-sulforaphane is described, which makes use of the pseudo-tetrahedral complex fragment [CpRu-(CHIRAPHOS)]+ as a chiral auxiliary. Reaction of the chloride complexes [CpRu(L-L)Cl] [L-L = 1,-bis(diphenylphosphino)ethane (dppe), (2S,3S)-and (2R,3R)-bis(diphenylphosphino)-butane ((S,S)- and (R, R)-CHIRAPHOS, respectively)] with phthalimidobutyl methyl sulfide gives the thioether complexes [CpRu(L-L)(MeSC4H8NPhth)]PF6. Oxygen transfer from dimethyldioxirane (DMD) produces the corresponding sulfoxide complexes in high yield and high diastereoselectivity. Cleavage of the phthaloyl group with aqueous hydrazine and subsequent reaction with thiophosgene yields the sulforaphane complexes [CpRu(L-L)(MeS(O)C4H8NCS)]PF6. Treatment of these with sodium iodide finally liberates the sulforaphane without noticeable racemization.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030510
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  • 103
    Electronic Resource
    Electronic Resource
    New Evidence for Conformational Flexibility in Cyclodextrins from Vibrational Raman Optical Activity (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1292-1298 
    Details
    ISSN: 0947-6539
    Keywords: carbohydrates ; conformation analysis ; cyclodextrins ; inclusion compounds ; Raman optical activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational flexibility in cyclodextrins (CDs) as a function of methylation, solvent interaction and the extent of inclusion complex formation has been studied by using vibrational Raman optical activity (ROA). The work exploited the sensitivity of ROA to skeletal mobility by comparing the intensity of the glycosidic ROA couplet between about 850 and 970 cm-1 in maltoheptose (MH), β-cyclodextrin (β-CD), heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) and heptakis(2,3,6-tri-β-methyl)-β-cyclodextrin (TM-β-CD) in buffered aqueous solution, in DMSO and with sodium benzoate and benzoic acid as guests in buffered aqueous solution. Increases in couplet signal strength were interpreted in terms of a reduction in conformational flexibility of the CD ring. In buffered aqueous solution the ROA intensity order MH 〈 TM-β-CD 〈 β-CD 〈 DM-β-CD was observed. The linear molecule MH is expected to be the most flexible of the four oligosaccharides studied, while the changes registered for the three CD macrocycles may be related to the degree of intramolecular hydrogen bond formation and its influence on conformational flexibility. In DMSO, the same ROA intensity order is observed, but with an approximately constant increase relative to the values obtained in aqueous solution. This can be explained by the tighter binding of DMSO in the CD cavities compared with H2O. For the inclusion complexes, our results indicate that the tighter the guest is bound, the larger is the reduction in the conformational flexibility of the CD macrocycle. The residual mobility sensed by ROA in CDs is similar to that sensed in proteins; this provides further insight into their analogous ligand-binding and catalytic properties.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030817
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  • 104
    Electronic Resource
    Electronic Resource
    5-exo-trig Versus 6-endo-trig Cyclization of Alk-5-enoyl Radicals: The Role of One-Carbon Ring Expansion (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 376-387 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; cyclizations ; cycloketones ; radicals ; ring expansions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alk-5-enoyl radicals were made to cyclize in exo and endo modes to give the corresponding cycloketone radicals, which are related through one-carbon ring expansion. Relative kinetic data were determined for the ring closure of the 2-methylhept-5-enoyl radical generated by the reaction of the corresponding phenylseleno ester with Bu3SnH over the temperature range 233-323 K. The conversion to absolute rates provided Arrhenius expressions for the 5-exo-trig and 6-endotrig cyclizations. Ab initio and semiempirical (AM1) calculations were performed on the hex-5-enoyl and hept-5-enoyl radicals, respectively, and the outcomes aided in the rationalization of the preexponential factors and activation energies. Both 1,5-and 1,6-ring closure occur via a lower energy “chairlike” transition state. The observed high regioselectivity is due to favorable entropic and enthalpic factors associated with the formation of the smaller ring. The stereoselectivity was higher in the 1,6-ring closure (70:30) than in the 1,5-ring closure (55:45), the trans isomer being predominant in both. For the onecarbon ring expansion studies, the radicals of interest were obtained by deoxygenation of suitable alcohols via the O-phenyl thiocarbonates with (TMS)3-SiH. The one-carbon ring expansion in the cyclopentanone series for the secondary alkyl radicals was studied over the temperature range 343-413 K by means of free-radical clock methodology and yielded the Arrhenius expression. The rate constant was 4.2 x 103 s-1 at room temperature and the reverse reaction (ring contraction) was found to be at least 10 times slower. Since the intermediacy of acyl radicals can be excluded, the reaction must occur via 3-membered cyclic intermediate radicals (or transition states).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030309
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  • 105
    Electronic Resource
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    A Novel Palladium-Catalyzed Asymmetric Cyclocarbonylation of Allylic Alcohols to γ-Butyrolactones (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 417-423 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric synthesis ; butyrolactones ; carbonylations ; catalyst system ; palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A catalyst system based on [Pd2(dba)3]·CHCl3/(-)-BPPM has been found to effect asymmetric cyclocarbonylation of certain prochiral allylic alcohols to produce good yields of optically enriched γ-butyrolactones. The reaction was performed under an atmosphere of H2 (400 psi) and CO (400 psi) at 100°C in methylene chloride for 48 hours. Asymmetric cyclocarbonylation of allylic alcohols with aliphatic substituents proceeded with moderate enantioselectivities (ee = 25-43%). However, enantiomeric excesses of up to 83% were obtained for substrates containing aromatic substituents, in which case the ee was found to be more sensitive to steric, rather than to electronic factors. Recrystallization of the lactones containing an aromatic group from a mixture of CH2Cl2/Et2O/hexanes (0.5/1.0/8.5), by slow evaporation of the solvent or at low temperature, improved the enantiopurities to 〉98% ee on a reproducible basis. The asymmetric center of the aromatic lactones was assigned the (S)-configuration based on the X-ray crystal structure analysis of enantiopure (S)-(+)-3,3-dimethyl-2-(2′-methylphenyl)-γ-butyrolactone (2k). A hydridopalladium intermediate is believed to play a key role in this reaction. Enantioselectivity is thought to be brought about by the preferential formation of 6b. The carbon skeleton of 6b fits into the chiral scaffold of (-)-BPPM.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030313
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  • 106
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    A New Strategy for Oligosaccharide Assembly Exploiting Cyclohexane-1,2-diacetal Methodology: An Efficient Synthesis of a High Mannose Type Nonasaccharide (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 431-440 
    Details
    ISSN: 0947-6539
    Keywords: carbohydrates ; glycoproteins ; HIV oligosaccharides ; protecting groups ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-mannose nonasaccharide 1 is part of the glycoprotein gp 120 of the viral coat of HIV-1. The mannan portion of this triantennary glycan was prepared by a number of consecutive glycosidation steps without the need for any protecting-group manipulation. This was achieved by carefully tuning the reactivity of the glycosyl donors by employing our cyclohexane-1,2-diacetal (CDA) methodology. The method was further extended with one-pot procedures for oligosaccharide synthesis, thus reducing the number of steps to form the protected nonasaccharide 21 from the monosaccharide building blocks to five.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030315
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  • 107
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    The N3 Position of N9-Substituted Adenine as a Metal Ion Binding Site: Structural and Solution Studies with PdII and PtII Complexes of N6′, N6′,N 9-Trimethyladenine (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 388-398 
    Details
    ISSN: 0947-6539
    Keywords: acid-base equilibria ; adenine palladium ; platinum ; structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Steric blockage of the N1 and N7 sites of 9-methyladenine for metal complexation is achieved by twofold methylation of the exocyclic amino group. With 6′,6′,9-trimethyladenine (TrimeA), binding of MII(dien) (M = Pt, Pd) as well as of trans-[Pt(NH3)2Cl]+ therefore takes place through N 3. X-ray crystal structure determinations and NMR spectroscopic studies of three compounds are reported, and the effects of PtII and PdII on the geometry and the acid-base properties of the TrimeA ligand have been measured and compared with those of the free base. TrimeA has a very pronounced self-stacking tendency in water (K=85M-1 according to the isodesmic model of indefinite noncooperative self-association). Acidity constants derived from potentiometric pH titrations, spectrophotometry, and NMR shift experiments display excellent agreement with each other. Twofold protonated TrimeA, that is H2(TrimeA)2+, carries protons at the N7 and N1 sites; the acidity constants are pKHH2(TrimeA) = - 0.75 and pKHH(TrimeA) = 4.15. These values compare well with those of other adenine residues. Protonation of [Pt(dien)-(TrimeA-N3)]2+ occurs at the N7 position, as shown by spectrophotometry and NMR spectroscopy. The acidity constant of the H+ (N7) site in this complex is low, that is pKHH[Pt(dien)(TrimeA)] = 0.3 (as determined by spectrophotometry), but it is not as low as that for the same site when a proton resides at N1 of unmetalated TrimeA. The pKa of the doubly protonated complex, pKHH2[Pt(dien)(TrimeA)], in which the second acidic proton is situated at N1, is about-1.2 ± 0.3. These findings indicate that upon metalation of N3, the sequence of adenine protonation is reversed. While the N7 site still displays basic properties, the N1 site has undergone a dramatic loss in basicity.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030310
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  • 108
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    Olefin Cross-Metathesis with Monosubstituted Olefins (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 441-444 
    Details
    ISSN: 0947-6539
    Keywords: alkenes ; allylsilanes ; C-C coupling ; cross-metathesis ; jasmonates ; molybdenum ; ruthenium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability of olefin cross-metathesis for the synthesis of different unsymmetrically substituted functionalized olefins is described. The coupling of different functionalized olefins in the presence of Grubbs' ruthenium catalyst or Schrock's molybdenum catalyst afforded the crossed products in good yields and with very high selectivities. Derivatives of jasmonic acid and functionalized allylsilanes were prepared by this catalytic method for carbon-carbon double bond formation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030316
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  • 109
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    Organic Approaches to Endohedral Metallofullerenes: Cracking Open or Zipping Up Carbon Shells? (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1009-1016 
    Details
    ISSN: 0947-6539
    Keywords: alkynes ; cobalt ; endohedral metallofullerenes ; fullerenes ; macrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have been investigating the synthesis of endohedral metallofullerenes since we successfully opened an orifice on the framework of C60 in the form of a cobalt complex having the metal sitting on top of the opening. A second approach aims at the synthesis of spherically-shaped acetylenic macrocycles, which are expected to rearrange to endohedral metal complexes of fullerenes in a controlled process analogous to the gas-phase coalescence of mono- and polycyclic polyynes during fullerene formation by the graphite evaporation method. Since the potential benefits from obtaining endohedral metal complexes of C60 are enormous, both approaches are being actively pursued in our group.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030705
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  • 110
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    Design and Synthesis of Sugar-Responsive Semiartificial Myoglobin Triggered by Modulation of Apoprotein-Cofactor Interactions (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1025-1031 
    Details
    ISSN: 0947-6539
    Keywords: boronic acids ; heme proteins ; molecular recognition ; myoglobin ; saccharides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenylboronic acid groups as sugar recognition sites were successfully introduced into native myoglobin by a cofactor-reconstitution method. Spectrophotometric pH titration demonstrated the sugar-induced pKa shift of the H2O coordinated to the heme center of the semisynthetic myoglobin bearing phenyl-boronic acids (met-Mb(PhBOH)2). By means of circular dichroism (CD) and paramagnetic 1H NMR spectroscopies, it was proven that sugars that were bound to phenylboronic acid sites induced the rearrangement of the heme crevice to reinforce the heme cofactor-apoprotein interactions. The structural changes that were induced by the binding of sugars subsequently enhanced the dioxygen storage activity of Mb(PhBOH)2. Such sugar-induced structural and functional changes did not occur for other modified Mbs that had no sugar-recognition units. Interestingly, a randomly modified Mb with phenylboronic acid units did not show any sugar response. In Mb(PhBOH)2, the information from the sugar-binding event was efficiently transmitted to the active center, so that the activity was efficiently altered upon sugar binding. In conclusion, the active site specific incorporation of molecular recognition units as nonnatural functional molecules can provide a novel strategy for the design of stimuli-responsive semisynthetic proteins.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030707
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  • 111
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    Allylsilanes as Carbon Nucleophiles in the Palladium-Catalyzed 1,4-Oxidation of Conjugated Dienes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 482-490 
    Details
    ISSN: 0947-6539
    Keywords: allylsilanes ; catalysis ; cyclizations ; oxidations ; palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Palladium-catalyzed oxidation of cyclic 1,3-dienes 3, 5, 9, 11, and 13, with an allylsilane group in the side chain, led to an intramolecular 1,4-syn-addition to the conjugated diene through a carbocyclization. Acyclic trienesilanes 7 also underwent analogous 1,4-oxidations. The reaction was carried out in acetone-acetic acid (2:1) with a slight excess of LiCl. p-Benzoquinone was employed as the oxidant and Li2PdCl4 as the catalyst. The reaction proceeds through an intramolecular trans addition of the allylsilane to a (π-diene)palladium complex to produce a bicyclic (π-allyl)palladium intermediate. Subsequent trans attack by chloride at the π-allyl intermediate gives the product. The intermediate (π-allyl)palladium complex was isolated and fully characterized. It was unambiguously demonstrated that the allylsilane had attacked the coordinated double bond trans to palladium (trans-carbopalladation). The use of CuCl2 as the oxidant, instead of p-benzoquinone, gave a less stereoselective addition, but interestingly, with the opposite stereochemistry.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030320
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  • 112
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    Studying the Stability of a Helical β-Heptapeptide by Molecular Dynamics Simulations (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1410-1417 
    Details
    ISSN: 0947-6539
    Keywords: helical structures ; molecular dynamics simulations ; NMR spectroscopy ; peptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Peptides consisting entirely of homochiral β-amino acids R-CH(NH2)-CH2CO2H form 31-helices in solution, as shown previously by NMR analysis of pyridine and methanol solutions. The stability of the helical secondary structure of one such β-peptide (H-β-HVal-β-HAla-β-HLeu-(S,S)-β-HAla(αMe)-β-HVal-β-HAla-β-HLeu-OH, 1) has been investigated by molecular dynamics simulations using the GROMOS 96 molecular model and force field (962 methanol molecules; T = 298, 350, 400 K; with and without NOE distance restraints). The restraints derived from the NMR studies were equally well satisfied by both the restrained and the unrestrained room-temperature molecular dynamics simulations. The 31-helical conformation of 1 was shown to be so stable that it was restored spontaneously within 400 ps after unfolding had been induced by a sudden increase of the temperature from 298 to 350 K.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030907
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  • 113
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    The Role of Backbone Oxygen Atoms in the Organization of Nucleic Acid Tertiary Structure: Zippers, Networks, Clamps, and C-H…O Hydrogen Bonds (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1400-1404 
    Details
    ISSN: 0947-6539
    Keywords: DNA structures ; hydrogen bonds ; nucleic acids ; RNA ; tertiary structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tight packing between structural elements is a prerequisite for molecular recognition and catalysis. In proteins, α-helices and β-sheets present the amino acid side chains on the surface while the polar amide bonds are buried. The opposite is found in double- and polystranded nucleic acids, where negatively charged phosphates occupy the surface and the side chains are hydrogen bonded in the core. Thus the question arises: How do densely packed nucleic acid molecules achieve close approach, despite the repulsion between phosphates that would appear to preclude tight contacts? One obvious answer is by mediating interstrand contacts through coordinated cations that can screen the negative charges. In this contribution, however, we highlight a variety of alternative direct interactions involving atoms of the sugar-phosphate backbone that can promote tight packing of RNA and DNA into functional molecules. We have analyzed the existing nucleic acid crystal structures in terms of the presence of close contacts between backbone regions. In RNA, ribose 2′-hydroxyl groups were observed to mediate such contacts in the majority of cases. However, their absence in DNA does not prevent oligodeoxynucleotides from packing tightly, aided by various interactions between backbone atoms.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030905
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  • 114
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    π-Electron Ring-Current Effects in Multiple Adducts of 3He@C60 and 3He@C70: A 3He NMR Study (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1071-1076 
    Details
    ISSN: 0947-6539
    Keywords: fullerenes ; endohedral helium complexes ; NMR spectroscopy ; ring currents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis- to hexakisadducts of C60 (1-6) and mono- to tetrakisadducts of C70 (7-13) containing 3He atoms (endo-hedral helium complexes) were prepared and studied by 3He NMR spectroscopy to determine the influence of degree of functionalization and addition pattern on the chemical shift of the 3He atom. In the series of C60 derivatives, which included the previously measured 6-6 monoadduct 3He@C61H2, the 3He resonance was shifted considerably upfield relative to that of 3He@C60 (δ = -6.36) up to the bisadduct 1 (δ = -11.45). The resonances of the higher adducts 3-6, however, were shifted only slightly further up-field and all appeared in a rather narrow spectral range between δ = -11.84 and -12.26. The absence of further substantial upfield shifts was rationalized in terms of the compensation of deshielding due to the functionalization-induced decrease in the diamagnetic π-electron ring currents that extend around the fullerene sphere by the shielding that results from the weaker pentagonal-ring paramagnetic currents and the increased number of localized benzenoid substructures in 3-6. In contrast, all 3He resonances of the C70 adducts are shifted downfield relative to the signal of 3He@C70 (δ = -28.81). A monotonic relationship exists between the chemical shift and the degree of functionalization, whereby the 3He chemical shifts steadily decrease from monoadduct 7 (δ = -27.53) to the isomeric tetrakisadducts 12 (δ = -21.09) and 13 (δ = -20.68). This deshielding was explained by the reduction of the strong diamagnetic ring currents extending along the polar corannulene perimeters as a result of the functionalization at α- and β-type polar bonds in 7-13. In both series, the addition pattern was also found to have a distinct influence on the 3He chemical shift.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030714
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  • 115
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    Dicyanopolyynes: A Homologuous Series of End-Capped Linear sp Carbon (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1105-1112 
    Details
    ISSN: 0947-6539
    Keywords: ab initio calculations ; alkynes ; carbon allotropes ; electronic structure ; semiempirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, isolation, spectroscopic characterization, and computational investigations of the rod-shaped dicyanopolyynes 1-6 (C2nN2, n = 4-9), which are model substances for the hypothetical one-dimensional carbon allotrope carbyne sp-C∞, are described. Based on the trends in the spectroscopic behavior of 1-6 with increasing chain length, the electronic as well as the NMR properties of carbyne are predicted. For the investigation of the synthetic potential of this compound class, a first selected series of regioselective derivatizations is presented with the synthesis of the [4+2] and [3+2] cycloadducts 7-12.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030718
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  • 116
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    Molecular and Supramolecular Synthesis with Dibenzofuran-Containing SystemsMolecular meccano, part 18; for Part 17, see D. B. Amabilino, P. R. Ashton, S. E. Boyd, M. Gómez-López, W. Hayes, J. F. J. Org. Chem. 1997, 62, 3062-3075. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1136-1150 
    Details
    ISSN: 0947-6539
    Keywords: crystal engineering ; dibenzofuran ; molecular quadrilaterals ; supra-molecular chemistry ; template synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The template-directed syntheses of two new tetracationic cyclophanes, cyclobis(paraquat-2,8-dibenzofuran) and cyclobis(paraquat-3,7-dibenzofuran), incorporating dibenzofuran subunits has been accomplished. Initially, the cyclophanes were self-assembled around a macrocyclic polyether template, bis-p-phenylene[34]crown-10 (BPP34C10), to form catenanes: the mechanical bond order of the catenane formed determined the requisite “amacrocyclic” templates for synthesis of the free cyclophane. X-ray crystallography shows that both of the cyclophanes possess rectangular covalent frameworks. Furthermore, these cyclophanes form self-assembled tapes in the solid state, since the dibenzofuran moieties have a tendency to associate with each other through crossed ∞-∞ stacks. The dibenzofuran-containing catenanes also form two-dimensional supramolecular arrays in the solid state on account of extended ∞-∞ stacking interactions. In addition, the serendipitous discovery of a plerotopic tecton (consisting of a dibenzofuran nucleus covalently linked from the 2- and 8-positions by methylene groups to 4,4′-pyridylpyridinium (hydrogen bond acceptor) and protonated bipyridinium (hydrogen bond donor) units) has been made. The tecton dimerizes in the solid state to form a supramolecular macrocycle, since its complementary hydrogen bonding sites are oriented in a horseshoelike fashion by the 2,8-disubstituted dibenzofuran unit. However, this superstructure is not retained in the 1:1 complex of the tecton with BPP34C10: cocrystallization of the tecton with this crown ether opens the macrocyclic two-component supermolecule to afford a hydrogen-bonded pseudopolyrotaxane.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030720
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    The C60 Core: A Versatile Tecton for Dendrimer Chemistry (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 561-567 
    Details
    ISSN: 0947-6539
    Keywords: conformation ; dendrimers ; fullerenes ; molecular dynamics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, complete characterization and molecular dynamics simulations of dendrimers 4-8 involving [60]fullerene as core tecton and first- to thirdgeneration benzyl-ether-based dendrons as branches is described. In dendrimer 7 a core branching multiplicity of 12, the highest known to date, is realized for the first time with a Th-symmetrical C60 core having an octahedral addition pattern. This unique structural type of core building block is only possible on the base of C60 and has no precedent in organic chemistry. NMR investigations as well as molecular modelling studies show that, owing to high core branching multiplicity, dendrimer 7 and to a minor extent the mixed adduct 8 already represent globular and densely packed macromolecules, although only first-generation dendrons are involved in their construction.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030411
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    Adsorption of Ionophores and of Their Cation Complexes at the Water/Chloroform Interface: A Molecular Dynamics Study of a [2.2.2]Cryptand and of Phosphoryl-Containing Podands (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 552-560 
    Details
    ISSN: 0947-6539
    Keywords: extraction ; interfaces ; ionophores ; molecular dynamics ; counterion effect ; solvation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report molecular dynamics simulations on ionophores of different topologies and on their complexes with alkali and alkaline-earth cations, with or without counterion, at the water/chloroform interface. As ionophores we consider two phosphoryl-containing podands (the “chainlike” monopodand MP and the “octopuslike” tripodand TP) and the bicyclic cryptand 222. We find that all the solutes behave as surfactants: they remain adsorbed at the interface, without migrating to bulk phases. Their precise location and solvation depend on the nature and conformation of the ionophore, of the cation and of the counterion. Schematically, two types of solutes can be distinguished, depending on their hydrophilic/hydrophobic character. The first type (cryptand 222 and its complexes, or the [MP⋅K+] complex), which have a hydrophobic exterior, stay on the chloroform side of the interface and are partially hydrated by “water fingers”. The second type (free MP and TP, [MP⋅K+]Pic- and [MP⋅Sr2+](Pic-)2 complexes), which are more hydrophilic, are partitioned to a greater extent between the two liquid phases. The status of the ion pairs at the interface depends on the interplay between cation … anion and anion … solvent interactions. When cation-anion interactions are strong enough (as in [MP⋅Sr2+](Pic-)2), the ion pairs remain intimate. Otherwise they dissociate, leading to solvent-separated ion pairs adsorbed at the interface (in the [222⋅K+] Pic- complex) or to the migration of the anion to the water phase (in the [222⋅K+] Cl- complex).
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030410
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    Functionalized Lipid Tubules as Tools for Helical Crystallization of Proteins (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 620-625 
    Details
    ISSN: 0947-6539
    Keywords: helical structures ; lipids ; liposomes ; self-assembly ; tubules ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The development of functional supramolecular devices built by self-assembly of elementary molecules and with bioactive properties arouses considerable interest in the field of nanotechnology and new materials. We report here the formation of a new class of lipid tubules exhibiting both properties of molecular recognition and crystal formation for the protein streptavidin. These lipid tubules, made of biotin-containing dioctadecylamine molecules, are straight hollow cylinders with a constant diameter of 27 nm and variable length up to several micrometers. They are unilamellar with an inner diameter of about 16 nm, as shown by cryoelectron microscopy. Streptavidin binds to the biotinylated tubules and assembles spontaneously into ordered helical arrays at the tube surface. These crystals exhibit regular order up to about 1.5 nm resolution. In addition, the helical streptavidin arrays act as functionalized supramolecular devices that bind a wide variety of biotinylated objects, as demonstrated here with proteins and liposomes.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030419
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997) 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030502
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    Calix[4]arene-Based (Hemi)carcerands and Carceplexes: Synthesis, Functionalization, and Molecular Modeling Study (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 639-654 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; carcerands ; inclusion compounds ; molecular devices ; resorcinarenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 11 calix[4]arene-based carceplexes obtained by solvent or doped inclusion is reported. Carceplexes with amides, for example, DMF, NMP, and 1,5-dimethyl-2-pyrrolidinone, and sulfoxides, for example, DMSO and thiolane-1-oxide, were obtained by solvent inclusion. In these cases the yield of the carceplex decreases with increasing guest size. Potential guests that do not form carceplexes by solvent inclusion, such as 2-butanone and 3-sulfolene, could be incarcerated by doped inclusion with 1,5-dimethyl-2-pyrrolidinone as a solvent “doped” with 5-15 vol% of potential guest. The amide bridges of the carceplexes were converted into thioamide bridges in essentially quantitative yield by means of Lawesson's reagent in refluxing xylene. The dynamic properties of the incarcerated guests were examined by 2D NMR spectroscopy. Whereas for most guests a preference for one orientation inside the calix[4]arene-based (thia)carcerands was observed, for DMA, NMP, and ethyl methyl sulfoxide inside calix[4]arene-based (thia)carcerands two different orientations were present. The energy barriers for interconversion between the various orientations of DMA, NMP, and ethyl methyl sulfoxide inside calix[4]arene-based (thia)-carcerands were determined with 2D EXSY NMR. The energy barriers are higher for the thiacarcerands than for the corresponding carcerands with amide bridges. This may be due to the stronger hydrogen-bond-donating character of the thioamide group. Furthermore, molecular modeling simulations indicate that in case of the thiacarcerand the cavity is smaller as a result of a smaller diametrical distance between the NH atoms. Our results demonstrate that molecular modeling can be used to estimate the energy barriers for interconversion; the calculated activation energies showed good quantitative agreement with the experimental values.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030421
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    Control of the Helical Chirality in Octahedral Complexes by a Chiral Macrobicyclic Cavity Possessing Six Convergent Hydroxyl Groups (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 969-973 
    Details
    ISSN: 0947-6539
    Keywords: chirality ; coordination modes ; macrocyclic ligands ; octahedral complexes ; supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (aR, aR, aR) and (aS, aS, aS) enantiomers of a chiral macrobicyclic ligand with a bicapped tris(binaphthol) structure were synthesized. Complexation of gallium(III), chromium(III) and iron(III) centres in the chiral cavities of these two ligands yielded exclusively one octahedral configuration in each case: the (aR, aR, aR) enantiomer gave a A complex and the (aS, aS, aS) enantiomer a complex. These assignments were established by CD spectroscopy for chromium and iron centres and by molecular modelling.
    Additional Material: 4 Ill.
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    Cover page (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. cpi 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030701
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    Graphical abstract (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 999-1003 
    Details
    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030703
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    Synthesis of Glycodendrimers by Modification of Poly(propylene imine) DendrimersSynthetic carbohydrate dendrimers, part 3. For part 2, see: P. R. Ashton, S. E. Boyd, C. L. Brown, N. Jayaraman, J. F. Stoddart, Angew. Chem. Int. Ed. Engl. 1997, 36, issue 7. A list of abbreviations used in this paper is given in ref. [37]. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 974-984 
    Details
    ISSN: 0947-6539
    Keywords: carbohydrates ; dendrimers ; glycosides ; neoglycoconjugates ; polymers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of preformed poly-(propylene imine) dendrimers (DAB-dendr-(NH2)x) for the rapid and facile construction of high molecular weight carbohydrate-coated dendrimers (glyco-dendrimers) is presented. An efficient attachment of spacer-armed derivatives of D-galactose and lactose to the primary amino end groups of DAB-dendr-(NH2)x has been achieved by means of amide bond formation, using the N-hydroxysuccinimide coupling procedure. Acetate protecting groups have been employed in order to avoid side reactions at the coupling stage. Deacetylation leads to the target glycodendrimers. The reactivity of all the available DAB-dendr-(NH2)x (generations 1-5) has been investigated and a series of homologous carbohydrate-coated dendrimers have been synthesized. In addition, the attachment of larger saccharide moieties has been demonstrated by the condensation of a trisgalactoside cluster with DAB-dendr-(NH2)x carrying both four and eight primary amino groups. The regularity of the glycodendrimers has been proven by NMR spectroscopy, and the molecular weights of the low-generation carbohydrate-coated dendrimers have been determined by mass spectrometry. Modifications of DAB-dendr-(NH2)x with biologically active carbohydrates affords a new and simple approach to high molecular weight compounds that may be considered as neoglycoconjugates with perfectly symmetrical structures and that offer much promise as multivalent ligands involved in carbohydrate-protein interactions.
    Additional Material: 6 Ill.
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    Trapping of Radicals in the Coordination Spheres of Metals (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1005-1008 
    Details
    ISSN: 0947-6539
    Keywords: alkali metals ; calcium ; ketyl radicals ; radicals ; samarium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of hexamethylphosphoramide (HMPA) or other sterically demanding groups as stabilizing ligands allows the successful isolation of a series of structurally characterizable complexes of ketyl radicals with alkali, alkaline earth, and lanthanide metal. It has been demonstrated that the stability and reactivity of the ketyl radicals strongly depend on both the nature of the metals to which they are bound and the steric and electronic properties of the ancillary ligands, as well as the structure of their parent ketones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970030704
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    Indium-Mediated Reactions of Enamines in the Presence of Acid (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1064-1070 
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    ISSN: 0947-6539
    Keywords: allylations ; enamines ; iminium salts ; indium ; zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of enamines with allyl bromide and metallic indium in THF to afford homoallylamines was greatly accelerated by the addition of one equivalent of a suitable carboxylic acid, such as acetic acid. It was established that the likely mechanism consists of a nucleophilic addition of an indium sesquihalide to the iminium salt formed by protonation of the enamine. Substituted allyl bromides also reacted with complete allylic transposition (γ-addition). In contrast to indium-mediated allylation of carbonyl compounds in which only two of the three allyl groups of the sesquihalide are involved, all three allyl groups are involved in the reaction with enamines. As a result only 2/3 equiv of indium are required. This allylation was also performed with zinc, tin, bismuth, and aluminum in the presence of a catalytic amount of InCl3 instead of indium. However, these reactions invariably gave lower yields. The analogous reaction of methyl bromoacetate instead of allyl bromide was also studied. This “Reformatsky-type” process was also greatly accelerated by the addition of one equivalent of acetic acid. In this case, the yields remained moderate for both indium and zinc.
    Additional Material: 4 Tab.
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    Effect of Melamine-Amphiphile Structure on the Extent of Two-Dimensional Hydrogen-Bonded Networks Incorporating Barbituric Acid (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1077-1082 
    Details
    ISSN: 0947-6539
    Keywords: amphiphiles ; barbituric acid ; hydrogen bonds ; melamines ; molecular recognition ; monolayers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four alkyl melamine amphiphiles each containing identical triads of hydrogen-bonding sites (hydrogen donor, acceptor, and donor) but different numbers of alkyl chains were examined in order to determine their monolayer properties and binding behavior towards barbituric acid (BA). Their structural organization in supramolecular assemblies at the air-water interface was affected by the bulkiness of the hydrophobic part of the amphiphile. Aqueous BA and amphiphiles with two or three alkyl chains formed a 1:1 alternate network structure. In contrast, a melamine amphiphile with four alkyl chains formed a 2:1 (BA:amphiphile) complex rather than a 1:1 alternate network structure. The 2:1 complex appears to behave like an independent molecular entity without further networking. The results point to the importance of size matching between the hydrophobic part of the monolayer and the underlying hydrogen-bonded network in order to maintain the overall supramolecular structure.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/chem.19970030715
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    Synthesis and Properties of O-Glycosyl Calix[4]Arenes (Calixsugars)This trivial name refers to calixarene derivatives in which one or more mono- or oligosaccharide moieties are bound to either the upper or lower rim by O-or C-glycosidic bond. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1774-1782 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; carbohydrates ; glycosylations ; host-guest chemistry ; Mitsunobu reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model O-glycosylation reactions at either rim of calix[4]arenes are described with the aim of providing access to a new family of carbohydrate-containing calixarene derivatives named calixsugars. One or two sugar moieties (D-mannofuranose and D-glucopyranose) were introduced at the lower rim of the parent calix[4]arene by glycosylation of the phenolic hydroxyl groups by means of a Mitsunobu reaction. Tetrapropoxy calix[4]arenes bearing two or four hydroxymethyl groups at the upper rim were coupled with perbenzoylated thioethyl D-galactoside and D-lactoside in the presence of the thiophilic promoter copper(III) triflate. In this way β-linked bis- and tetrakis-O-galactosyl calix[4]arenes were obtained in good yield, the latter showing some solubility in water. For the O-lactosyl derivatives only the bis-substituted compound could be obtained because of the competing formation of an intramolecular ether linkage between 1,3-hydroxymethyl groups. Preliminary binding studies showed some affinity of the galactose-containing calixsugars toward charged carbohydrates and dihydrogen phosphate anion.
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    Synthesis, Structure and Hydrolysis Studies of Dimethyltris(Trimethylsilyl)Methylmetallanes of Aluminium and GalliumDedicated to Professor Manfred Weidenbruch on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1783-1792 
    Details
    ISSN: 0947-6539
    Keywords: aluminium ; gallium ; hydrolyses ; Si ligands ; structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of [(Me3Si)3CLi2thf] with Me2MCl (M = Al, Ga) afford the mixed trialkylmetallanes [(Me3Si)3-CAlMe2·thf] (1) and [(Me3Si)3 CGaMe2·thf] (2) in high yields. The coordinated THF molecule of compound 2 can be removed by sublimation in vacuo to yield the solvent-free product [(Me3Si)3-CGaMe2] (3). Hydrolysis of compound 2 with one equivalent of water at 0°C gives the trimeric hydroxide [{(Me3Si)3CGaMe(μ-OH)}3] (4), while the reaction with two equivalents of water at room temperature yields the unusually stable gallium hydroxide-water complex [{(Me3Si)3CGaMe(OH)(μ-OH)MeGaC(SiMe3)3) H2O·2thf] (6). On heating, compound 6 is converted to the hydroxide [{(Me3Si)3C}4Ga4(μ-O)2(μ -OH)4] (5), which has a heteroadamantane-like core. The hydrolysis of compound 1 with one equivalent of water at - 25°C gives the dimeric hydroxide [{(Me3Si)3CAlMe(μ-OH)}2·2thf] (7), while the reaction with two equivalents of water results in the formation of the novel hydroxide [{(Me3Si)3C}4Al4(μ-O)2 (μ-OH)4] (8), which is isostructural to the gallium compound 6 with the adamantane-like structure. The molecular structures of compounds 1, 2, 4, 5·3THF, 6, 7 and 8·0.5 THF have been determined by X-ray structure analysis. Compound 7 is the first structurally characterised aluminium hydroxide containing methyl groups, and 8 is the smallest structurally characterised galloxane hydroxide described in literature.
    Additional Material: 7 Ill.
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    Intermediates in the Catalytic Dehydrogenative Coupling of Arylgermanes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1793-1796 
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    ISSN: 0947-6539
    Keywords: dehydrogenative coupling ; germanium ; platinum ; reaction mechanisms ; structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of a new electron-withdrawing germane, H2Ge[3,5-(CF3)2C6H3]2 (3), has facilitated the isolation and characterization of three new complexes implicated in the dehydrogenative coupling of bisarylgermanes by Pt0-phos-phane complexes. The intermediates include a digermyl species, trans-[(Et3P)2Pt{GeH(Ar)2}2] (7), a bound digermane showing the first stage of Ge-Ge catenation, cis-[(Et3P)2Pt(H){Ge(Ar)2-GeH(Ar)2}] (8), and the Ge-H activated form of this product, [(Et3P)2HPtGe(Ar)2-Ge(Ar)2PtH(PEt3)2] (6). Complexes such as 6 and 8 have not previously been isolated as intermediates in dehydrogenative coupling reactions. An X-ray crystal structure was determined for complex 6, confirming the cis geometry of the hydrogen and germanium ligands; this provides yet another example of the stability of germyl hydrides towards reductive elimination. A similar cis geometry was observed for complex 8. Performing the dehydrogenative coupling reaction under a CO2 atmosphere failed to yield any products containing trapped germylene species.
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    Two New Closely Related MoV Hydroxymonophosphates Built Up of Cd[Mo6P4O25(OH)6]2 And Cd[Mo6P4O26(OH)5]2 ClustersDedicated to Professor H. G. von Schnering on the occasion of his retirement (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1797-1800 
    Details
    ISSN: 0947-6539
    Keywords: cadmium ; crystal structure ; hydrothermal synthesis ; hydroxyphosphate ; molybdenum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new molybdenum(v) hydroxyphosphates have been synthesized hydrothermally, Na2Cd3(Mo2O4OH)6-(PO4)2(PO3OH)6[N(CH3)4]4·10H20 (1) and Cd9(Mo2O4OH)12(PO4)6(PO3OH)10-[N(CH3)4]8·15H2O (2). Their structures have been determined from single-crystal X-ray diffraction. The water molecules and hydroxyl groups have been deduced from valence calculations. Both compounds crystallize in the triclinic space group P1, with the cell parameters for 1 a = 12.340(2), b = 12.596(1), c = 14.717(2) Å, α = 107.24(1)°, β = 89.83(1)°, γ = 114.31(1)°, V = 1972.3(4) Å3, and for 2 a = 11.942(1), b = 13.339(2), c = 26.765(3) Å, α = 85.33(1)°, β = 86.87(1)°, γ = 64.08(1)°, V = 3821.3(9) Å3. The two frameworks can be described on the basis of similar [Mo6P4X31]n- (X = O, OH) anionic clusters, but 1 is a tridimensional structure, whereas 2 exhibits a monodimensional structure.
    Additional Material: 5 Ill.
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    Aggregation, Reaggregation and Degradation of a Trifunctional Thallium(I) Amide Induced by Weak TlI ⃛ TlI AttractionDedicated to Professor Mary McPartlin on the occasion of her 65th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1801-1806 
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    ISSN: 0947-6539
    Keywords: aggregations ; amides ; metal-metal interactions ; subvalent compounds ; thallium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal exchange of the solvated tripodal lithium amide [H3CC{CH2N(Li-solv)SiMe3}3] (1, solv = ether solvent) with thallium(I) chloride leads to the previously reported pentametallated dimeric thallium amide [{H3CC(CH2NSiMe3)3}2(H)Tl5] (2) in high yield. That the redox-induced partial demetallation of the amide presumably occurs at an intermediate stage of the metal exchange is inferred from the isolation and structural characterization of the mixed Tl-Li amide [H3CC{CH3N(Tl) SiMe3}3][H3CC{CH2NSiMe3}3(H)(Tl)(Li-thf)]·(toluene) (3), which has a crystal structure closely related to that of 2. In both cases the central structural motif, defined by weakly attractive Tl⃛ Tl contacts, is a tetrahedral metal array in which a triangular thallium triamide unit is capped by an exposed Tl atom of a second building block. Compound 3 may be converted to 2 by metal exchange with TlCl. The two supramolecular components of 2 reaggregate upon recrystallization in a nonpolar solvent such as pentane to yield the dimeric aggregate of the fully metallated thallium amide [H3CC{CH2N(Tl)-SiMe3}3]2 (4). An X-ray crystallographic study of 4 established the existence of dimeric aggregation through Tl ⃛ Tl interactions leading to a more open dimeric form than 2 and 3, which is interpreted as being due to a structural mismatch of the building blocks. Compound 4 may be thermally degraded by prolonged stirring in toluene at ambient temperature to yield the previously reported mixed-valence TlITlII amide [H3CC(CH2NSiMe3)3Tl2] (5).
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    Biomimetic Crystallization of Calcium Carbonate Polymorphs by Means of Collagenous Matrices (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1807-1814 
    Details
    ISSN: 0947-6539
    Keywords: aragonite ; biomineralization ; calcite ; crystal growth ; peptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crosslinked gelatin films with entrapped poly-L-aspartate were used to induce the crystallization of calcite and aragonite polymorphs. Calcite with high degrees of isomorphous substitution (up to 12mol% magnesium) has been obtained. The morphology and layered organization of magnesium calcite crystals grown inside the crosslinked gelatin films with entrapped poly-L-aspartate resemble some structural features of radial calcitic ooids. The concentration of entrapped poly-L-aspartate and the uniaxial deformation of the films control the growth of aragonite aggregates inside the films. Such aggregates grown inside uniaxially deformed films consist of parallel rods with an architectural assembly similar to that found in some marine organisms. The crystals' aggregation and the control of calcium carbonate polymorphism are related to the modelling of the nucleation sites by poly-L-aspartate structure and concentration, local supersaturation and microenvironment shape. The results indicate that the collagenous matrices with entrapped polyelectrolytes are versatile systems which can contribute to the elucidation of strategies for biomimetic materials chemistry.
    Additional Material: 7 Ill.
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    Calix[4]Arene Podands and Barrelands Incorporating 2,2″-Bipyridine Moieties and Their Lanthanide Complexes: Luminescence Properties (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1815-1822 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; lanthanides ; luminescence ; molecular dynamics ; N ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new family of cone-shaped podands and barrel-shaped cryptands based on calix[4]arenes incorporating 5,5′-substituted 2,2′-bipyridine subunits were prepared and characterized. The Eu3+ and Tb3+ complexes of the podands bearing two, three, or four bipyridine chromophores could be isolated. High molar absorption coefficients (εmax = 39 600M-1 cm-1 for Eu4 and 26 700M-1 cm-1 for Eu3) and high metal luminescence quantum yields (16% for Eu4 and 15% for Eu3) were obtained. Molecular dynamics simulations on Eu4 showed that the bipyridine arms wrap around the lanthanide cation, efficiently shielding the cation from solvent molecules. In the presence of chloride counter-ions the fourth bipyridine arms does not coordinate the lanthanide ion. Ligands bearing two bipyridine units and two additional functional groups - ethyl butyrate or N-propylpyrrole - did not give stable lanthanide complexes. The barre-land containing two calix[4]arene moieties and four bipyridine groups did not form complexes with lanthanide ions, most probably because of the rigidity of the ligand.
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    Noncovalent Assembly of Functional Groups on Calix[4]Arene Molecular Boxes (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1823-1832 
    Details
    ISSN: 0947-6539
    Keywords: calixarenes ; hydrogen bonds ; molecular boxes ; noncovalent assembly ; supramolecular chemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calix[4]arenes diametrically substituted at the upper rim with two melamine units spontaneously form well-defined box-like assemblies in the presence of two equivalents of 5,5-diethylbarbituric acid. These assemblies, consisting of nine different components, are held together by 36 hydrogen bonds and are stable in apolar solvents at concentrations of up to 10-4M. This paper reports the first X-ray crystal structure, and the MALDI TOF mass spectra together with the complete 1H NMR spectroscopic characterization of these hydrogen-bonded assemblies. The crystal structure clearly shows that the assemblies are stereogenic, as a result of the antiparallel orientation of the two rosette motifs. Furthermore, the synthesis of twelve new 1,3-bis(melamine)calix[4]arenes carrying different numbers and types of functionalities at the upper rim is described. Detailed 1H NMR spectroscopic studies on the assembly behavior of these functionalized calix[4]arenes shows that 1) polar substituents (e.g. nitro, cyano) hardly affect the stability of the hydrogen-bonded assembly; 2) hydrogen bond donating or accepting groups, like amino and acetamido, can disturb assembly of the boxes under certain conditions by destabilizing the calix[4]arene pinched cone conformation as a result of intramolecular hydrogen bond formation; and 3) sterically bulky groups (e.g. tBu) can significantly inhibit the formation of the hydrogen-bonded assembly, but this effect very much depends on the exact positions of the groups.
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    Zinc(II)-Catalyzed Disproportionation in Rubber: The mechanism of Sulfur Vulcanization Revisited (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1846-1851 
    Details
    ISSN: 0947-6539
    Keywords: disproportionations ; dithiocarba-mate ; homogeneous catalysis ; vulcanization ; zinc ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Model studies have shown that cross-link precursors, that is, intermediates in the sulfur vulcanization of rubber, are transformed into cross-links by a nonsymmetric but regioselective disproportionation mechanism. Thus, two equivalents of the crosslink precursor of the type R—S—S—X are transformed into X—S—X and the actual cross-link R—S—S—S—R. Exchange of sulfur atoms is a prerequisite. A mechanism involving an SNi′ reaction with an allylic moiety, suggested in the literature, has not been observed. The disproportionation reaction is catalyzed by rubber-soluble zinc-dithiocarbamate complexes, an important class of vulcanization accelerators. By virtue of ligand-functional-group exchange reactions these complexes serve to transport and exchange sulfur atoms.
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    URL: http://dx.doi.org/10.1002/chem.19970031117
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    Stoichiometric and Catalytic Reactions of the Polysiloxane-Bound (Ether-Phosphine)Rhodium(I) Complex [ClRh(PO)(P ∼ O)] in InterphasesSupported organometallic complexes part 14. Part 13: E. Lindner, A. Jäger, F. Auer, W. Wielandt, P. Wegner, J. Mol. Catal. in press.Dedicated to Professor H. D. Kaesz on the occasion of his 65th birthdayNotation used in this paper: Fn = functionality; D, T, and Q denote alkoxysilanes with two, three, and four Si-O bonds, respectively; the superscript denotes the number of Si—O—Si bonds formed during the sol-gel process and is a measure of cross-linkage; for example, T0 = MeSi(OMe)3. P∼O: η1-P-coordinated ether-phosphine ligand; PO: η2-O,P-chelating ether-phosphine ligand. Cy = cyclohexyl, COE = cyclooctene, Py = pyridine. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1833-1845 
    Details
    ISSN: 0947-6539
    Keywords: immobilized catalysts ; polysiloxanes ; P ligands ; rhodium ; sol-gel processes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of four equivalents of the monomeric trimethoxysilyl(T)-functionalized ether-phosphine ligand CyP(CH2CH2OCH3)(CH2)3SiR3 (R = OMe [1 a(T0)], Me [1 b]) with [{μ-ClRh(COE)2}2] yielded the monomeric pseudo 14 electron rhodium(I) complexes [ClRh(PO)(P∼O)] (2a(T0)2, 2 b). For the sol-gel process the complex 2 a(T0)2 was protected by introduction of the volatile, reversibly binding ligand pyridine. Thus, the monomeric compound 2 a(T0)2 was co-condensed with two and eight equivalents of the co-condensation agent MeSi(OMe)2(CH2)6(MeO)2SiMe (D0-C6-D0) to give the polysiloxane-bound congeners 2(Tn)2(Di-C6-Di)y (y = 2 and 8, respectively; i = 0-2; n = 0-3). The polysiloxane-bound complex 2(Tn)2-(Di-C6-Di)2 was treated with a variety of small molecules in the gas/solid and liquid/solid interphases. It was shown that a facile cleavage of the Rh-O bond in the ether-phosphine chelate occurred even in the solid state. The reaction of 2(Tn)2-(Di-C6-Di)2 with carbon monoxide, carbon disulfide, and diphenylacetylene resulted in the irreversible coordination of the molecule to the metal. In the presence of pyridine, the polysiloxane-bound complex 2(Tn)2-(Di-C6-Di)2 oxidatively added hydrogen to give the octahedrally configurated complex [ClRhH2(Py)(P ∼ O)2] [6(Tn)2(Di-C6-Di)2]. Treatment of dry 2(Tn)2-(Di-C6-Di)2 with ethene led to the reversible formation of the corresponding complex. Although the materials display low surface areas, at least 75% of the rhodium centers within the matrix are accessible to the rather bulky tolan molecules. The complexes 2(Tn)2(Di-C6-Di)y (y (y = 2, 8) show high activities and selectivities in the hydrogenation of tolan. The conversion was found to depend markedly on the amount of co-condensate (D0-C6-D0) and on the polarity of the solvent. The polysiloxane-bound complexes 2(Tn)2(Di-C6-Di)y are more active than their monomeric congener 2 a(T0)2.
    Additional Material: 8 Ill.
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    Gold Clusters and Colloids in Alumina NanotubesDedicated to Professor Achim Müller on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1951-1956 
    Details
    ISSN: 0947-6539
    Keywords: clusters ; colloids ; gold ; nanostructures ; quantum wires ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fabrication of a supported and insulated quantum wire would be of great interest, especially if electronic information could be accessed to determine charging and conductivity profiles. The feasibility of forming one-dimensional configurations of ≈ 15 nm gold colloids and 1.4 nm gold clusters via template methods of synthesis has now been demonstrated. The template host material consisted of porous alumina membranes formed by an electrochemical anodic process. The pores of the membrane, and hence the parallel pore channels, were packed in a hexagonal array. Alumina membranes are excellent template materials because of their high degree of order, thermal and chemical stability, and optical clarity. Pore diameter was controlled by regulation of the applied anodic potential (ca. 1.4 nm V-1). The pore channels were filled by one of three methods: vacuum induction (colloids only), electrophoresis (clusters only), or immersion (clusters, which were then converted into colloids by heating). Rudimentary wires consisting of colloids and clusters were successfully formed. In both cases, the diameter of the pore channel exceeded that of the clusters or colloids. The wires thus formed conformed to the pore channel by forming helical secondary structures. It was not possible to form contiguous wires of clusters by immersion, or of colloids formed from clusters after heating. Composites (consisting of the gold-alumina system) were a bright scarlet color with an absorption maximum (λmax) at 519.5 nm. This is an unexpected result for spherical and small-diameter (10 nm) gold colloids, which normally absorb at λmax 525-530 nm, a ruby-red color. Possible causes of this small but remarkable blue shift are discussed below. A new Au55 cluster ligand system consisting of a silsesquioxane-derivatized thiol is also described.
    Additional Material: 11 Ill.
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    Total Synthesis of Oxazole- and Cyclopropane-Containing Epothilone B Analogues by the Macrolactonization Approach (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1971-1986 
    Details
    ISSN: 0947-6539
    Keywords: epothilone ; oxazoles ; cyclopropanes ; total synthesis ; macrolactonizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to probe structure-activity relationships in the epothilone area, two series of epothilone B analogues have been designed and synthesized. The first series containing an oxazole moiety in place of a thiazole on the side chain was constructed by utilizing key intermediates 7-9 or 10, 12, and 13 (Scheme 1), whereas the second series containing an ethano group instead of the gem-dimethyl group at position 4 was synthesized from fragments 42 and 43. A Yamaguchi-type macrolactonization reaction was used to construct the macrocycle from a secoacid, which was assembled, in both cases, by means of a) an aldol reaction, b) an Enders alkylation, and c) a Wittig-type reaction. This convergent strategy provided access to oxazole analogues 2,4,29-32 and 4,4-ethano derivatives 3,40,60-63 for biological studies.
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    Polymeric [(Me3Sn)3Rh(SCN)6]: A Novel “Super-Prussian-Blue” Derivative Containing the Nonlinear -SCN-Sn-NCS- SpacerDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1987-1991 
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    ISSN: 0947-6539
    Keywords: coordination polymers ; Prussian blue ; rhodium ; structure elucidation ; tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new coordination polymer [(Me3SnIV)3RhIII(SCN)6] = 3∞[Rh{μ-(SCNSnMe3NCS)}3] (5) is readily accessible by straightforward self-assembly of [Rh(SCN)6]3- and (dehydrated) {Me3Sn}+aq ions. The architecture of 5 is strongly reminiscent of “super-Prussian-blue” systems reported earlier: there is a three-dimensional (3-D) framework involving {Rh8} pseudocubes as the basic building blocks, the Rh3+ ions being held apart by novel, nonlinear {SCN-SnMe3-NCS} spacers (d(Rh…Rh) = 1.27 nm). The complete lattice consists of two equivalent and independent, ideally interwoven 3-D frameworks. Three homologues of 5 with slightly modified R3Sn units (R = Et, nPr and nBu) have been prepared as well, but display X-ray powder diffraction patterns notably different from that of 5.
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    Electrochemically Induced Molecular Motions in Pseudorotaxanes: A Case of Dual-Mode (Oxidative and Reductive) Dethreading (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1992-1996 
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    ISSN: 0947-6539
    Keywords: cyclic voltammetry ; logic gates ; molecular devices ; pseudorotaxanes ; spectroelectrochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical and spectroscopic properties of a pseudorotaxane formed in acetonitrile solution by self-assembly of a wire-type electron donor based on the tetrathiafulvalene unit and the cyclobis(paraquat-p-phenylene) tetracationic electron acceptor have been investigated. We show that a) reversible dethreading/rethreading cycles of the pseudorotaxane can be performed by either oxidation and successive reduction of the electron-donor wire or reduction and successive oxidation of the electron-accepting tetracationic cyclophane, and b) because of this special behavior, the input (electrochemical)/output (absorption spectrum) characteristics of this molecular-level system correspond to those of an XNOR logic gate.
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    Oligonucleotide Analogues with 4-Hydroxy-N-Acetylprolinol as Sugar Substitute (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1997-2010 
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    ISSN: 0947-6539
    Keywords: antisense agents ; chiral recognition ; oligonucleotides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modified oligonucleotides incorporating trans-4-hydroxy-N-acetyl-L-prolinol (trans-4-HO-L-NAP) or its D-analogue as sugar substitute were synthesised with adenine and thymine as nucleobases. All-adenine oligonucleotides built from (2S,4S) or (2R,4R)-cis-4-hydroxy-N-acetylprolinol were likewise prepared. Hybridisation studies revealed that heterocomplexes formed between polyU and homochiral trans-4-hydroxy-N-acetylprolinol-based oligomers of the same as well as of opposite chirality (polyU/trans-DA*13 and polyU/trans-LA*13). The former, however, were triple-stranded. Other complexes with ribonucleic acids were polyA/trans-LT*13 and polyU/cis-LA*13. Heteroduplexes with deoxynucleic acids were formed between trans-LA*13 and oligothymidylate. Interaction was also observed for cis-LA*13 and oligothymidylate, but not with the D-hydroxyprolinol analogues. Microcalorimetry proved this interaction to be the formation of a triple-stranded complex. Two heteroduplexes, trans-LA*13/dT13 and trans-LA*13/polyU, had similar or slightly increased stability when compared to the natural dA13/dT13 or dA13/polyU systems. Microcalorimetry clearly indicated the formation of a duplex, in contrast to interactions with N-acetylprolinol oligonucleotides of different stereochemistry. Moreover, the enthalpy change was of the same magnitude but the association constant was slightly lower. Natural nucleic acids thus clearly prefer hybridisation with L-hydroxyprolinol oligomers over D-hydroxyprolinol oligomers. For the series investigated, the L-trans oligomers (Figure 1) seem best to mimic natural oligonucleotides. These modified oligonucleotides formed homocomplexes if both strands were of the same chirality, that is, homocomplexes formed between trans-LA* and trans-LT* and between trans-DA* and trans-DT*, reflecting the isochiral pu-py pairing found in natural nucleic acids. Once more, however, calorimetry proved these to be triplex interactions. Heterochiral pairing was not observed between modified oligonucleotides, but only between modified oligonucleotides and natural polyU. The thermal stabilities of these heterochiral complexes differed clearly.
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    Rapid Coupling of Methyl Iodide with Aryltributylstannanes Mediated by Palladium(0) Complexes: A General Protocol for the Synthesis of 11CH3-Labeled PET Tracers (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2039-2042 
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    ISSN: 0947-6539
    Keywords: arylphosphanes ; C-C coupling ; isotopic labeling ; palladium ; tin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of methyl iodide and (excess) aryltributylstannane to give a methylarene has been studied with the focus on the realization of rapid coupling for incorporation of short-lived radionuclides into bioactive organic compounds. The coupling of methyl iodide with tributylphenylstannane (40 equiv) is accomplished in 〉90% yield within 5 min at 60°C with a tri-o-tolylphosphine-bound, coordinatively unsaturated Pd0 complex together with a CuI salt and K2CO3 in DMF. This protocol is applicable to a variety of homo- and heteroaromatic tin compounds, to give the corresponding methylated derivatives. The effects of the tri-o-tolylphosphine ligand, a Cu(I) salt, and DMF are discussed. This new protocol provides a firm chemical basis for the synthesis of 11CH3-incorporated PET tracers.
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    Mechanisms and Stereochemistry of Acid-Induced Ring Opening of Optically Active 1,2-Propene Oxides in the Gas PhaseChiral ions in the gas phase, part 3. Parts 1 and 2: ref. [1]. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 2063-2070 
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    ISSN: 0947-6539
    Keywords: chirality ; gas-phase chemistry ; ion-molecule reactions ; regioselectivity ; ring-opening reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The acid-induced ring opening of (S)-( - )-1,2-propene oxide (1S) and (R)-(+)-1,2-propene oxide (1R) has been investigated in gaseous CH4 and CH3F at 720 torr and in the presence of a nucleophile, NuOH (Nu = H or CH3). The mechanism of the ring-opening reaction has been assessed by modulating the composition of the gaseous mixture. Two reaction pathways are operative in the gas phase, both proceeding through complete inversion of configuration of the reaction center. A first process is detectable only in the CH3F/H2O systems and takes place within a persistent proton-bound complex generated by interaction of the epoxide with the CH3OH+2 ion, formed by methylation of H2O with (CH3)2F+. Such an intracomplex ring-opening pathway proceeds through proton transfer from the CH3OH+2 ion to the epoxide followed by motion of the neutral CH3OH moiety around the 1-H-oxonia-2-methyl-cyclo-propane structure (H-1R or H-1S) (k〈108 s-1) before attacking the ring carbons from the rear. In all the other systems with added CH3OH, this intracomplex pathway is preceded by a faster “extracomplex” pathway involving the attack of an external CH3OH molecule on the proton-bound adduct. The regioselectivity of the intracomplex process is similar to that of the extracomplex pathway. Both are characterized by a slight preference for the Cβ center of H-1 R (or H-1S) (extra-complex path regioselectivity: α/β = 0.72±0.05; intracomplex path regioselectivity: α/β = 0.71±0.05). The regioselectivity of H-1 R (or H-1S) is substantially different from that of the 1-Me-oxonia-2-methyl-cyclopropanes (Me-1 R or Me-1 S) toward the same nucleophile NuOH (α/β = 4.1±0.35 (Nu = H); 2.28±0.16 (Nu = CH3)). This difference is attributed to a transition structure wherein the Cα-O bond rupture increases from H-1 R (or H-1 S) to Me-1 R (or Me-1 S) and in passing from CH3OH to H2O. The regioand stereoselectivity of the gas-phase acid-induced ring opening of 1 S and 1 R are compared with those of related reactions carried out in solution.
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    Cover page (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. cpi 
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    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 8 Ill.
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    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997) 
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    ISSN: 0947-6539
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031002
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    Chirality in Dendritic ArchitecturesThis concepts article is a personal reflection on the many issues raised by the combination of chirality and dendrimers. The concepts presented here are partly based on several recent reports in the published literature and partly on the highly appreciated discussions with colleagues on as yet undisclosed results. In particular Bert Meijer would like to express his gratitude to Professor Hans Wynberg who stimulated him to explore all aspects of stereochemistry.Dedicated to Professor Hans Wynberg on the occasion of his 75th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1563-1570 
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    ISSN: 0947-6539
    Keywords: catalysis ; chirality ; dendrimers ; molecular recognition ; surfaces ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: At first glance the topic of chiral dendrimers seems to be a contradiction in terms. However, recent studies reveal that both the building blocks of the dendrimer and the overall dendritic architecture can be chiral and that chirality can be introduced at various levels. The expression of optical activity in these enantiomerically pure dendrimers as a result of conformational (dis)order has proven to be of special interest. In this Concepts article we present the different approaches to introducing chirality in dendritic architectures, organized through their possible impact in fields such as biocompatibility, catalysis, molecular recognition, and surface chemistry. Also, the relation between molecular chirality of core or building block and the macroscopic chirality of dendritic objects is discussed.
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    URL: http://dx.doi.org/10.1002/chem.19970031005
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    Development of Tools for the Design of Selectin AntagonistsDedicated to Professor Hans Paulsen on the occasion of his 75th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1571-1578 
    Details
    ISSN: 0947-6539
    Keywords: carbohydrates ; molecular modeling ; preorganization ; sialyl Lewisx ; selectins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A molecular modeling tool for the rational design of E-selectin antagonists based on the lead structure sialyl Lewisx has been developed. The binding affinity to the receptor is considerably influenced by the entropy and consequently by the antagonist's ability to place its pharmacophores in an optimal spatial arrangement, i.e., by its preorganization for binding. The computational model assesses the preorganization of a potential selectin antagonist with the aid of Monte Carlo (jumping between wells)/stochastic dynamics [MC(JBW)/SD] simulations. The model has been validated by correlating preorganization and bioactivity of several selectin antagonists. The results suggest that only preorganized compounds are likely to bind to E-selectin.
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    Complex Formation of the Antiviral 9-[2-(Phosphonomethoxy)Ethyl]Adenine (PMEA) and of Its N 1, N 3, and N 7 Deaza Derivatives with Copper(II) in Aqueous SolutionAbbreviations and definitions: 2′-AMP2-, adenosine 2′-monophosphate; 3′-AMP2-, adenosine 3′-monophosphate; ATP4-, adenosine 5′-triphosphate; M2+, divalent metal ion; PA2- = PME2-, PMEA2-, and its twofold negatively charged deaza derivatives; R-PO2-3, simple phosphate monoester or phosphonate ligand with R representing a noncoordinating residue (see also Figure 1); TuMP2-, tubercidin 5′-monophosphate (=7-deaza-5′-AMP2-). Although the IUPAC nomenclature for the deazaadenine compounds is 3H-imidazo[4,5b]pyridine-7-amine (1-deazaadenine), imidazo[4,5c]pyridine-4-amine (3-deazaadenine), and pyrrolo[2,3d]pyrimidine-4-amine (7-deazaadenine), the trivial names and the numbering system for purines are retained in the present study to facilitate the comparison with the parent compound, PMEA2-, and other adenine derivatives. For example, 1-deaza-PMEA is thus named 9-[2-(phosphonomethoxy)ethyl]-1-deazaadenine. In mathematical expressions and tables, 1-, 3-, and 7-deaza-PMEA are written as 1d-, 3d-, and 7d-PMEA. In the text the expression „PMEAs“ encompasses PMEA as well as its three deaza derivatives. Species written without a charge either do not carry one or represent the species in general (i.e., independent of their protonation degree); which of the two possibilities applies is always clear from the context. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1526-1536 
    Details
    ISSN: 0947-6539
    Keywords: adenine ; isomerizations ; NMR spectroscopy ; nucleotides ; stability constants ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants of the 1:1 complexes formed between Cu2+ and the anions of the N 1, N 3, and N 7 deaza derivatives of 9-[2-(phosphonomethoxy)-ethyl]adenine (PA2-), Cu(H;PA)+ and Cu(PA), were determined by potentiometric pH titration in aqueous solution (25 °C; I = 0.1 M, NaNO3) and compared with previous results for 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA2-) and (phosphonomethoxy)ethane (PME2-). A microconstant scheme reveals that in Cu(H;PA)+ Cu2+ is coordinated to the nucleobase, H+ being at the phosphonate group, in about 90% of the Cu(H;PMEA)+ and Cu(H;1-deaza-PMEA)+ species, but only in about 37% and 12% of the corresponding complexes with H(3-deaza-PMEA)- and H(7-deaza-PMEA)-, respectively. Straight-line plots of log KCuCu(R-PO3) versus pKHH(R-PO3) for simple phosph(on)ate ligands show that all the Cu(PA) complexes, including those with PMEA2- and PME2-, are more stable than expected simply from the basicity of the -PO2- group; to some extent five-membered chelates (Cu(PA)cl/O) involving the ether oxygen of the -CH2-O-CH2-PO2-3 chain are formed, and in all complexes an additional nucleobase-metal-ion interaction occurs. Based on 1H NMR line-broadening measurements and structural considerations it is concluded that in Cu(3-deaza-PMEA) the interaction occurs with N7 whereas in Cu(7-deaza-PMEA), Cu(1-deaza-PMEA), and Cu(PMEA) it occurs with N3. The proof of a metal ion-N3 interaction is important (and also of relevance regarding DNA) because so far this interaction has received little attention. In all Cu(PA) systems three major isomeric species are in equilibrium; for example, 17(∓3)% of Cu(PMEA) exists as an isomer with a sole Cu2+-phosphonate coordination, 34(∓10)% as Cu(PMEA)cl/O, and in 49(∓10)% the Cu2+ is bound to the phosphonate group, the ether O, and N3. In contrast, 54(∓8)% of Cu(5′-AMP) occurs as an isomer with sole Cu2+-phosphate coordination and 46(∓8)% as a macrochelate involving N7 too.
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    The Versatility of Lithium Reagents in Synthetic Organometallic Chemistry: Their differing reactions with [Cp*Mo(NO)(CH2SiMe3)2] (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1579-1587 
    Details
    ISSN: 0947-6539
    Keywords: alkylidene complexes ; lithium ; molybdenum ; nitric oxides ; tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [Cp*Mo(NO)(CH2SiMe3)2] exhibits three principal types of reaction with the various lithium reagents investigated during this study, namely: regioselective deprotonation, reduction, and addition. Deprotonation of the reactant, achieved by treatment with lithium amide reagents, leads ultimately to the formation of the alkylidene „ate“ complex [Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3] (1). While LiN(SiMe3)2 effects this conversion directly with no detectable intermediates, reaction with 1 equiv of LDA in THF for 15 min deprotonates the Cp* ligand to form the lithium salt of the „tucked-in“ ate complex [(η5,η1-C5Me4CH2)Mo(NO)(CH2SiMe3)2]-[Li(thf)3] (2) in 40% isolated yield. Complex 2 slowly converts to the thermodynamically more stable 1 when left as a THF or C6D6 solution at ambient temperature for 48 h. Reaction of the dialkyl starting material with either tBuLi or PhLi leads to the production of the alkylidene complex 1 in irreproducible yields (10-50% NMR; not isolable). A kinetic analysis of the reaction of [Cp*Mo(NO)(CH2SiMe3)2] with LiN(SiMe3)2 indicated that the reaction was first-order in both the lithium and molybdenum reagents, and the activation parameters of ΔH* = 7.3∓1.0 kcal mol-1 and ΔS* = - 34∓3 e.u. suggest an associative process. Treatment of the neutral dialkyl with 1 equiv of LiPPh2 in THF results in a one-electron reduction and production of {[Cp*Mo(NO)(CH2SiMe3)2[Li2(thf)3] (3). If left in solution, the 17e- dialkyl anion 3 is converted to the 18e- alkylidene anion 1 by the Ph2P-PPh2 coproduct, which effects the requisite hydrogen-atom abstraction. Finally, addition of a sterically undemanding alkyllithium reagent such as MeLi to the 16e- dialkyl reactant leads to the formation of the 18e- trialkyl anionic complex [[Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3](Me)][Li(thf)3] (4). Warming of 4 in a C6D6 solution results in loss of methane and production of 1. In most cases, the chemistry exhibited by the Mo system is duplicated by the analogous W congener, [Cp*Mo(NO)(CH2SiMe3)2(=CHSiMe3)]2-[Li2(thf)3]. The solid-state molecular structures of complexes 1 and 4 have been established by single-crystal X-ray crystallographic analyses.
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    Cope Rearrangements versus Retro Diels-Alder ReactionsAzo Bridges from Azines, part 25; for part 24 see U. Brand, S. Hünig, K. Peters, F. Prokschy, H. G. von Schnering, Liebigs Ann. 1997, 785-789.Dedicated to Professor Dr. Dieter Seebach on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1588-1599 
    Details
    ISSN: 0947-6539
    Keywords: azo compounds ; cycloadditions ; hydropyridazines ; pyrazolines ; rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two isomeric [4+2] cyclo-adducts from two different 1,3-dienes may result from direct cycloadditions as well as from Cope rearrangements (Scheme 1). This general question is tackled by employing two energetically different types of dienes, protonated pyrazolines (1H+, 2H+) or dihydropyridazines (3H+), prepared in situ from their trimers and alicyclic (4-6) or aliphatic (7-9) 1,3-dienes. Depending on structural features and conditions (amount of acid, reaction time), various ratios of the two isomeric [4+2] cycloadducts A and B are obtained; A and B are azo compounds 10, 14, 16, 20, 22, 24, 27, 32, 34, 36-39, 41, 42, pyrazolines endo-11, endo-13, endo-15, endo-endo-17, endo-18, endo-19, 21, 23, 25, 26, 28, and hydropyridazines 31, endo-33, endo-35, 40 and 43 (Schemes 3, 4). These results were backed by others from acid-catalyzed isomerizations, trapping experiments, and calculations of the equilibria (ΔΔH) between the isomers (by analogy with the corresponding olefins). A critical discussion reveals: a) Azo compounds 20, 22, 24, 27, 34, 38, and 42 must result from a [4++2] cycloaddition with inverse electron demand, whereas hydropyridazines endo-33, endo-35, 40, and 43 originate from a [4+2+] cycloaddition with normal electron demand. b) All isomerizations occur by a [3,3] sigmatropic rearrangement; [4+2] cycloreversion is energetically disfavored. c) A clear-cut distinction between the [4++2] or [4+2+] cycloaddition reaction routes to the energetically well-balanced systems 10→endo-11 and 12→endo-13 is not possible. d) The two cycloadditions may well favor a nonconcerted reaction through an allylic cationic intermediate which also governs the [3,3] rearrangements (Scheme 8).
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    Type B Semiconductor Photocatalysis: The Synthesis of Homoallyl Amines by Cadmium Sulfide-Catalyzed Linear Photoaddition of Olefins and Enol/allyl Ethers to N-Phenylbenzophenone ImineHeterogeneous Photocatalysis, part XVI. Part XV: W. Schindler, H. Kisch, J. Photochem. Photobiol. A: Chem., 1997, 103, 257. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1638-1645 
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    ISSN: 0947-6539
    Keywords: cadmium sulfide ; catalysis ; photochemistry ; semiconductors ; unsaturated amines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homoallyl amines were synthesized by visible-light irradiation of CdS powder in the presence of N-phenylbenzophenone imine and cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, 3,4-dihydropyran, 2-pentene, cyclopentene, 1-methylcyclohexene, or α-pinene. The structures of the products from the last three olefins were determined by single-crystal X-ray analysis to prove that C-alkylation of the imine had occurred. Thus, the reaction is formally an insertion of the imine into an allylic C-H bond of the olefin. It is proposed that a photogenerated electron-hole pair reduces the imine to an α-aminodiphenylmethyl radical and oxidizes the olefin with concomitant deprotonation to the corresponding allyl radical. Heterocoupling of these intermediates affords the final addition product. The overall reaction is therefore classified as type B semiconductor photocatalysis. The presence of acetic acid accelerates the reaction by rendering the reduction potential of the imine more positive. In the series 2,5-dihydrofuran/cyclopentene/3,4-dihydropyran, the decrease in apparent quantum yield with increasing driving force of olefin oxidation points to a significant contribution of secondary back electron transfer.
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    Mammalian cell death proteases: A family of highly conserved aspartate specific cysteine proteases (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 33-42 
    Details
    ISSN: 0730-2312
    Keywords: apoptosis ; cysteine proteases ; CPP32 ; Mch2 ; Mch3 ; Mch4 ; Mch5 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: So far nine human aspartate-specific cysteine proteases (ASCPs) have been identified and cloned in our lab and others. Their sequence and structural homology to the nematode Ced-3 implicated them in the cell death pathway of mammalian cells. Recent evidence suggests that ASCPs initiate apoptosis by acting at or near the cell death effector level. However, it is not clear whether the activity of one or several of these enzymes is necessary for execution of apoptosis. In addition, it is not yet clear how the proenzymes of ASCPs are activated or what triggers their activation. Execution of apoptosis in higher eukaryotes is apparently more complicated than in nematodes. It is most likely that in mammalian cells this process involves the coordinated action of multiple ASCPs and multiple redundant proteolytic pathways. J. Cell Biochem. 64:33-42. © 1997 Wiley-Liss, Inc.
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    Osteogenic differentiation of purified, culture-expanded human mesenchymal stem cells in vitro (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 295-312 
    Details
    ISSN: 0730-2312
    Keywords: osteoblast ; glucocorticoids ; hydroxyapatite ; osteoprogenitor ; bone marrow ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Human bone marrow contains a population of cells capable of differentiating along multiple mesenchymal cell lineages. Recently, techniques for the purification and culture-expansion of these human marrow-derived Mesenchymal Stem Cells (MSCs) have been developed. The goals of the current study were to establish a reproducible system for the in vitro osteogenic differentiation of human MSCs, and to characterize the effect of changes in the microenvironment upon the process. MSCs derived from 2nd or 3rd passage were cultured for 16 days in various base media containing 1 to 1000 nM dexamethasone (Dex), 0.01 to 4 mM L-ascorbic acid-2-phosphate (AsAP) or 0.25 mM ascorbic acid, and 1 to 10 mM β-glycerophosphate (βGP). Optimal osteogenic differentiation, as determined by osteoblastic morphology, expression of alkaline phosphatase (APase), reactivity with anti-osteogenic cell surface monoclonal antibodies, modulation of osteocalcin mRNA production, and the formation of a mineralized extracellular matrix containing hydroxyapatite was achieved with DMEM base medium plus 100 nM Dex, 0.05 mM AsAP, and 10 mM βGP. The formation of a continuously interconnected network of APase-positive cells and mineralized matrix supports the characterization of this progenitor population as homogeneous. While higher initial seeding densities did not affect cell number or APase activity, significantly more mineral was deposited in these cultures, suggesting that events which occur early in the differentiation process are linked to end-stage phenotypic expression. Furthermore, cultures allowed to concentrate their soluble products in the media produced more mineralized matrix, thereby implying a role for autocrine or paracrine factors synthesized by human MSCs undergoing osteoblastic lineage progression. This culture system is responsive to subtle manipulations including the basal nutrient medium, dose of physiologic supplements, cell seeding density, and volume of tissue culture medium. Cultured human MSCs provide a useful model for evaluating the multiple factors responsible for the step-wise progression of cells from undifferentiated precursors to secretory osteoblasts, and eventually terminally differentiated osteocytes. J. Cell. Biochem. 64:295-312. © 1997 Wiley-Liss, Inc.
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    Mdm-2: “big brother” of p53 (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 343-352 
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    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: No abstract.
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    UVC activation of the HeLa cell membrane “TGFαASE,” a metalloenzyme (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 353-368 
    Details
    ISSN: 0730-2312
    Keywords: transforming growth factor α ; “TGFαase” ; ultraviolet radiation ; cell surface proteases ; HeLa cells ; membrane fragments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have investigated the effect of UVC irradiation on “TGFαase” activity using both intact HeLa cells and isolated membrane fragments with an assay based on the previously described nonapeptide substrate method [Brown et al. (1992): J Cell Biochem 48:411-423]. This method allows recognition of cleavage at the scissile bond cognate with that of the TGFα N-terminal cleavage site from its membrane-bound precursor. The level of ectoendopeptidase (including “TGFαase”) activity observed on intact cells was lower than that of ectoaminopeptidases. Addition of foetal bovine serum (FBS) enhanced aminopeptidase and dipeptidyl peptidase activity but inhibited “TGFαase” activity, while phorbol 12-myristate 13-acetate (PMA) had no significant effect on the ectopeptidases monitored, except for “TGFαase,” which was also inhibited, in contradistinction to their effects in other cell systems. Sublethal UVC irradiation (10 Jm 2) of the cultures resulted in activation of the ectoaminopeptidase and ectoendopeptidases which was maximal 16 and 20-24 h after irradiation, respectively. The addition of FBS to these irradiated cells appeared to reduce the increase in endopeptidase products, due in part to increased aminopeptidase activity but also to the direct inhibitory effect of FBS on the “TGFαase.” The activation of these proteases by UVC, even at high fluences (500 Jm 2), was not observed within the first 30 min after the cells were irradiated. Purified plasma membrane fragments were prepared from suspension cultures of HeLa cells and displayed high levels of “TGFαase” activity. The rate of “TGFαase” activity using 140 nM peptide substrate (P9) was 5.6 pmol/min/mg membrane protein, which was elevated to 13.7 pmol/min/mg membrane protein, 20 h after the cells had been irradiated with 10 Jm 2 UVC. Inhibition studies indicate that the plasma membrane “TGFαase” is a metalloenzyme, as it was inhibited by EDTA, EGTA, and 1,10-phenanthroline but not by elastase or serine protease inhibitors. “TGFαase” activity on intact cells was shown to be inhibited by 1,10-phenanthroline, which further supports this suggestion. Treatment of the membranes with Triton X-100 resulted in a loss of “TGFαase” activity, raising the possibility that this enzyme may require a cofactor to be fully functional. We show that in purified membrane preparations of HeLa cells there is evidence for the presence of a “TGFαase” which can be activated by UV irradiation, which differs from the putative “TGFαase” described in various other cell lines, and which does not seem dependent on protein kinase C (PKC) activity. J. Cell. Biochem. 64:353-368. © 1997 Wiley-Liss, Inc.
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    Phosphorylation of the carboxy-terminal repeat domain in RNA polymerase II by cyclin-dependent kinases is sufficient to inhibit transcription (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 390-402 
    Details
    ISSN: 0730-2312
    Keywords: carboxy-terminal repeat domain (CTD) ; RNA polymerase II ; cyclin-dependent kinases ; phosphorylation ; transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cdc2 kinase triggers the entry of mammalian cells into mitosis, the only cell cycle phase in which transcription is globally repressed. We show here that Cdc2 kinase phosphorylates components of the RNA polymerase II transcription machinery including the RNA polymerase II carboxy-terminal repeat domain (CTD). To test specifically the effect of CTD phosphorylation by Cdc2 kinase, we used a yeast in vitro transcription extract that is dependent on exogenous RNA polymerase II that contains a CTD. Phosphorylation was carried out using immobilized Cdc2 so that the kinase could be removed from the phosphorylated polymerase. ATPγS and Cdc2 kinase were used to produce an RNA polymerase 110 that was not detectably dephosphorylated in the transcription extract. RNA polymerase 110 produced in this way was defective in promoter-dependent transcription, suggesting that phosphorylation of the CTD by Cdc2 kinase can mediate transcription repression during mitosis. In addition, we show that phosphorylation of pol II with the human TFIIH-associated kinase Cdk7 also decreases transcription activity despite a different pattern of CTD phosphorylation by this kinase. These results extend previous findings that RNA polymerase 110 is defective in preinitiation complex formation. Here we demonstrate that phosphorylation of the CTD by cyclin-dependent kinases with different phosphoryl acceptor specificities can inhibit transcription in a CTD-dependent transcription system. J. Cell. Biochem. 64:390-402. © 1997 Wiley-Liss, Inc.
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    PDGF-BB increases endothelial migration and cord movements during angiogenesis in vitro (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 403-413 
    Details
    ISSN: 0730-2312
    Keywords: PDGF ; PDGF receptor ; cell migration ; endothelial cell ; endothelium ; angiogenesis ; in vitro ; urokinase-type plasminogen activator ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To explore direct effects of platelet-derived growth factor (PDGF) on endothelial cells during angiogenesis in vitro, we have used cloned bovine aortic endothelial cells that spontaneously form cord structures. Recently we have shown that cells forming these endothelial cords express PDGF β-receptors and that PDGF-BB can contribute to cellular proliferation and cord formation. In this study we investigated whether PDGF-induced cellular migration might also contribute to endothelial repair and angiogenesis in vitro.Ten individual endothelial cells in cords were tracked at an early stage of cord formation by video-timelapse microscopy. PDGF-BB (100 ng/ml) induced an increase in endothelial cell movement of 67 ± 15% as compared with diluent control. Interestingly, PDGF-BB also increased movements of entire cord structures, followed at branching points, by 53 ± 12% over diluent control. Taken together, these video-timelapse experiments suggested that the apparent movements of single endothelial cord cells might also be due to the motion of entire underlying cord structures in response to PDGF. To analyze the response of single endothelial cord cells we therefore examined whether PDGF-induced migration contributes to endothelial repair. Abrasions were applied with a razor blade to confluent monolayers of endothelial cells at an intermediate stage of cord formation. PDGF-BB concentration-dependently increased the distance to which cord-forming endothelial cells migrated into the abrasion. An increased number of elongated, i.e., probably migrating, endothelial cells was found in the abrasion in response to PDGF-BB. However, there was no effect of PDGF-BB on the total number of endothelial cells found in the abrasion. PDGF-AA affected neither the distance to which the cells migrated nor the number of elongated cells.Actin and tubulin stainings revealed that these cytoskeletal structures were not appreciably altered by PDGF-BB. Furthermore, urokinase-type plasminogen activator transcripts were not modulated in response to PDGF-BB.We conclude that in this model of angiogenesis in vitro PDGF-BB can elicit the movement of entire cord structures, possibly via u-PA-independent mechanisms. PDGF-BB also controls the migration of single cord-forming endothelial cells. Thus, PDGF-BB possibly contributes to endothelial repair and angiogenesis by direct effects on proliferation and composite movements of PDGF β-receptor-expressing endothelial cells and cords. J. Cell. Biochem. 64:403-413. © 1997 Wiley-Liss, Inc.
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    Basic FGF regulates interstitial collagenase gene expression in human smooth muscle cells (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 32-41 
    Details
    ISSN: 0730-2312
    Keywords: bFGF ; interstitial collagenase ; mRNA ; extracellular matrix ; atherosclerosis and restenosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Basic fibroblast growth factor (bFGF) is a mitogenic factor that is implicated in smooth muscle cell growth in atherosclerosis and vascular restenosis. In this study, we examined the effect of bFGF on the expression of the interstitial collagenase gene in human vascular smooth muscle cells. Results from Northern transfer analysis showed that bFGF increased collagenase mRNA levels greater than threefold as early as 24 h. Collagenase pre-mRNA levels were elevated approximately threefold by bFGF, according to RT-PCR analysis. Transient transfections of the smooth muscle cells with a 4.4-kb human collagenase promoter-CAT reporter gene, however, failed to show upregulation of the promoter activity by bFGF. Interestingly, transfections with deleted fragments containing promoter sequences from -1047 to -2271 resulted in modest stimulation of the collagenase-CAT promoter activity by bFGF. bFGF did not alter the stability of the collagenase mRNA, as demonstrated by degradation studies. The enhanced collagenase mRNA levels elicited by bFGF were reflected in increased amounts of collagenase protein that were detected by Western blot analysis. In summary, bFGF upregulates the interstitial collagenase expression, resulting in turnover of the extracellular matrix, an event that could facilitate smooth muscle cell migration and proliferation during the early stages of atherosclerosis and restenosis. J. Cell. Biochem. 65:32-41. © 1997 Wiley-Liss, Inc.
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    Dual transduction signaling by a Xenopus muscarinic receptor: Adenylyl cyclase inhibition and MAP kinase activation (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 75-82 
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    ISSN: 0730-2312
    Keywords: adenylyl cyclase ; MAP kinase ; G protein ; βγ subunit ; Xenopus oocyte ; signal transduction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Using transient transfection of COS-7 and human embryonic kidney 293 cells, we studied the functional properties of a previously cloned muscarinic Xenopus receptor [Herrera et al. (1994): FEBS Lett 352:175-179] and its coupling to adenylyl cyclase (AC) and mitogen-activated protein kinase (MAPK) pathways. Expression of the Xenopus muscarinic receptor results in the inhibition of AC activity and activation of the MAPK pathway through a mechanism that involves a Pertussis-sensitive G-protein and the Gβγ subunits. The signal transduction properties of this receptor are similar to the mammalian m2 and m4 muscarinic receptors. These results strongly support the idea that inhibition of AC and MAPK activation, signaled out from the muscarinic oocyte receptor, are involved in the oocyte maturation process. J. Cell. Biochem. 65:75-82. © 1997 Wiley-Liss, Inc.
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    Involvement of DNA methylation in the control of the expression of an estrogen-induced breast-cancer-associated protein (pS2) in human breast cancers (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 95-106 
    Details
    ISSN: 0730-2312
    Keywords: breast cancers ; genomic sequencing ; 5-methyldeoxycytidine ; multiple component analysis ; pS2 ; RT-PCR ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: pS2 gene has been used to investigate the relationship between alterations of DNA methylation patterns in human tumors and gene expression. The expression of pS2, which is transcriptionally controlled by estrogens in breast cancer cell lines, is restricted to estrogen-receptor-rich human breast tumors. We found that the CCGG site within the promoter/enhancer sequence of pS2 was hypomethylated in estrogen-receptor-rich breast tumors expressing this gene. The amount of DNA molecules unmethylated at this site was related to the amount of pS2 mRNA detected in the samples. The demethylation of this region, which contains the estrogen responsive element, was confirmed by genomic sequencing. Transient expression of functional human estrogen receptors stimulated the expression of the endogenous pS2 in HeLa cells, but failed, in BT-20 cells, to stimulate expression of this gene. Since the promoter/enhancer region of pS2 is unmethylated in HeLa cells and methylated in BT-20 cells, these data also support the hypothesis that DNA methylation might be involved in the control of pS2 expression. J. Cell. Biochem. 65:95-106. © 1997 Wiley-Liss, Inc.
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    Absence of cell-surface annexin V is accompanied by defective collagen matrix binding in the swarm rat chondrosarcoma (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 131-144 
    Details
    ISSN: 0730-2312
    Keywords: annexin V ; extracellular matrix ; cell surface ; chondrosarcoma ; chondrocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Annexin V has been characterized as a major collagen type II binding cell-surface component of normal chondrocytes and is also called anchorin CII in chondrogenic populations. Herein we present evidence that in vitro cultured Swarm rat chondrosarcoma cells are not capable of binding collagen type II in significant quantities to their surfaces, as compared to normal rat chondrocytes. This finding coincides with a deficiency of annexin V on the surface of these cells. A small quantity of an intracellular polypeptide could be detected which is immunologically cross-reactive with annexin V but displayed a mobility in SDS-PAGE of less than 34 kD compared to the Mr 36 kD of intact rat annexin V. By immunohistochemistry the protein could be localized in the cytoplasm of in vitro and in vivo grown tumor cells. By reverse transcription-polymerase chain reaction and Northern blot analysis, a regular-sized mRNA for annexin V could be detected in the chondrosarcoma cells that is expressed in only slightly lower quantities than in normal chondrocytes. Taken together, the data suggest a modified processing or turnover for annexin V in the chondrosarcoma excluding it from being a functionally active collagen type II binding protein. The findings support the hypothesis of cell-surface annexin V as a key component for the formation of the pericellular matrix of chondrocytes. J. Cell. Biochem. 65:131-144. © 1997 Wiley-Liss, Inc.
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    Fas stimulation induces RB dephosphorylation and proteolysis that is blocked by inhibitors of the ICE protease family (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 586-594 
    Details
    ISSN: 0730-2312
    Keywords: Fas ; apoptosis ; RB ; ICE ; protease ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Fas antigen is a member of the tumor necrosis factor/nerve growth factor receptor family. Stimulation of Fas by Fas ligand or agonistic antibodies results in the activation of interleukin-1β converting enzyme-like (ICE-like) proteases, and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP). Ultimately, Fas activation leads to apoptotic cell death. The importance of PARP cleavage to the death process remains unclear. We have hypothesized that the cleavage of other cellular substrates may be important for Fas-mediated apoptosis. Here we show that stimulation of Fas results in significant alterations of retinoblastoma protein (RB). Treatment of Jurkat cells, a human leukemic T cell line, with anti-Fas induces dephosphorylation of RB, followed by proteolytic cleavage. These events precede internucleosomal DNA fragmentation. Dephosphorylation and cleavage of RB are inhibited by a specific tetrapeptide inhibitor of ICE-like proteases or by expression of cowpox virus CrmA protein or the Bcl-2 oncoprotein. Inhibition of these RB changes correlates with inhibition of apoptosis. We propose that cleavage of RB may represent an important step in the pathway of Fas-mediated apoptotic cell death. J. Cell. Biochem. 64:586-594. © 1997 Wiley-Liss, Inc.
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    Effects of proteoglycan modification on mineral formation in a differentiating chick limb-bud mesenchymal cell culture system (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 632-643 
    Details
    ISSN: 0730-2312
    Keywords: calcification ; proteoglycans ; chondrocyte culture ; micro-mass culture ; cartilage calcification ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the presence of 4 mM inorganic phosphate, differentiating chick limb-bud mesenchymal cells plated in micromass cultures form a mineralized matrix resembling that of chick calcified cartilage. To test the hypothesis that cartilage proteoglycans are inhibitors of cell mediated mineralization, the synthesis, content, and turnover of proteoglycans were altered in this system, and the extent of mineralization and properties of the mineral crystals examined. In all cases where the proteoglycan synthesis or proteoglycans present were modified to provide fewer or smaller molecules, mineralization was enhanced. Specifically, when proteoglycan synthesis was blocked by treatment with 10-10 M retinoic acid, extensive mineral deposition occurred on a matrix devoid of both proteoglycans and cartilage nodules. The crystals, which formed rapidly, were relatively large in size based on analysis by X-ray diffraction or FT-IR microspectroscopy, and were more abundant than in controls. When 2.5 or 5 mM xylosides were used to cause the synthesis of smaller proteoglycans, the extent of mineral accretion was also increased relative to controls; however, the matrix was less affected, and the extent of mineral deposition and the size of the crystals were not as markedly altered as in the case of retinoic acid. Modification of existing proteoglycans by either chondroinase ABC or hyaluronidase treatment similarly resulted in increased mineral accretion (based on 45Ca uptake or total Ca uptake) relative to cultures in which the proteoglycan content was not manipulated. Crystals were more abundant and larger than in control mineralizing cultures. In contrast, when proteoglycan degradation by metalloproteases was inhibited by metal chelation with o-phenanthroline, the Ca accretion at early time points was increased, but as mineralization progressed, Ca accumulation decreased. These data provide evidence that in this culture system, proteoglycans are inhibitors of mineralization. J. Cell. Biochem. 64:632-643. © 1997 Wiley-Liss, Inc.
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    Aberrant expression and regulation of hepatic epidermal growth factor receptor in a c-myc transgenic mouse model (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 64 (1997), S. 651-660 
    Details
    ISSN: 0730-2312
    Keywords: TGF-α ; mitogenic signal ; tyrosine kinase activity ; SP1 ; transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In an attempt to elucidate the mechanism by which c-myc and transforming growth factor-α (TGF-α) cooperate in hepatocyte tumor development, we have analyzed signaling by the epidermal growth factor (EGF) receptor and the consequent regulation of receptor number in transgenic mice bearing the c-myc transgene under the control of the albumin enhancer/promoter. 125I-EGF binding and Scatchard analysis indicated a single class of high affinity receptors with the total number of binding sites of 1.2 × 104 ± 600 and 2.5 × 105 ± 1000 sites/cell in the normal and c-myc hepatocytes in primary culture, respectively. After 72 h of EGF exposure in culture, the number of detectable EGF receptors on the cell surface of the c-myc hepatocytes was not reduced, whereas the number of EGF receptors on normal hepatocytes was reduced to 32% that of untreated hepatocytes. Nuclear run-on experiments done with nuclei isolated from intact livers demonstrated that transcription of the EGF receptor was 4.9-fold higher in c-myc mice. Increased levels of the transcriptional factor SP1 in the c-myc hepatocytes in vivo and in primary culture, suggest a mechanism for the increased transcription of the EGF receptor. c-myc also increases the expression of TGF-α; a consequent increase in tyrosine phosphorylation is also detected in vivo. Thus, the increased number of EGF receptors in c-myc expressing hepatocytes, even after prolonged exposure to EGF, or TGF-α in vivo, may allow greater triggering of the EGF receptor signaling cascade. J. Cell. Biochem. 64:651-660. © 1997 Wiley-Liss, Inc. This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
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    Developmental regulation of osteocalcin expression in MC3T3-E1 osteoblasts: Minimal role of the proximal E-box cis-acting promoter elements (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 11-24 
    Details
    ISSN: 0730-2312
    Keywords: basic helix-loop-helix proteins ; E-box ; differentiation ; transcription ; transfection ; osteocalcin ; ld ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteoblasts undergo a temporal sequence of development characterized by transcriptional upregulation of osteoblast-specific genes. Basic helix-loop-helix (bHLH) transcription factors may control this developmental process through binding to E-box cis-acting elements in developmentally regulated genes. To investigate the role of bHLH proteins in MC3T3-E1 osteoblasts, which undergo a developmental sequence in vitro, we analyzed the transcriptional control of osteocalcin gene expression by stable transfection of an osteocalcin promoter-luciferase chimeric gene (p637OC-luc) and assessed the role of E-box cis-acting elements in osteocalcin promoter by DNA binding assays. We compared our findings in MC3T3-E1 osteoblasts with transient DNA transfections and DNA binding assays. We compared our findings in MC3T3-E1 osteoblasts with transient DNA transfections and DNA binding experiments in Ros 17/2.8 osteoblasts. We found that the activity of 637-OC luciferase promoter was low in undifferentiated 5-day-old cultures but increased in parallel with endogenous osteocalcin message expression in mature MC3T3-E1 osteoblasts, consistent with developmental stage-specific transcriptional upregulation of the osteocalcin gene. We identified two putative E-box elements in the proximal osteocalcin promoter, E-box 1 (CACATG) at - 102 and E-box 2 (CAGCTG) at position - 149. In gel mobility shift assays, factors present in nuclear extracts derived from differentiated osteoblast bound to oligonucleotide probes containing the E-box 1 and E-box 2 elements. Binding to the E-box 2 probe was not specific for the core CAGCTG element, whereas the CACATG site in E-box 1 oligonucleotide was required for specific binding of these nuclear factors. Stable transfection of p637OC-luc containing a mutant E1 site (p637OC-luc E1m), however, did not alter the developmental upregulation of osteocalcin promoter activity in MC3T3-E1 osteoblasts. Moreover, the E-box 1 mutation had no effect on either basal or vitamin D-stimulated activity of the osteocalcin promoter in Ros 17/2.8 osteoblasts in transient transfection experiments. These data suggest that osteoblasts contain undefined factors that bind to the E-box 1 CACATG site in the proximal osteocalcin promoter; however, this E-box element does not play a significant role in the developmental stage-specific regulation of the osteocalcin gene in MC3T3-E1 osteoblasts. J. Cell. Biochem. 65:11-24. © 1997 Wiley-Liss, Inc.
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    Nongenomic effects of an anti-idiotypic antibody as an estrogen mimetic in female human and rat osteoblasts (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 53-66 
    Details
    ISSN: 0730-2312
    Keywords: intracellular calcium ; Pertussis toxin-sensitive G-protein ; phospholipase C ; creatinine kinase ; gender-specificity ; antiestrogens ; estrogen mimetic ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We investigated the early effects of the anti-idiotypic antibody (clone 1D5), which recognized the estrogen receptor (ER), on cytosolic free calcium concentration ([Ca2+]i) and its long term effects on creatine kinase (CK) specific activity in female human and rat osteoblasts. These actions were compared to the known membrane and genomic effects of 17β estradiol (E2). Like E2, clone 1D5 increased within 5 s [Ca2+]i in both cell types by two mechanisms: 1) Ca2+ influx through voltage-gated Ca2+ channels as shown by using EGTA, a chelator of extracellular Ca2+, and nifedipine, a Ca2+ channel blocker; 2) Ca2+; mobilization from the endoplasmic reticulum as shown by using phospholipase C inhibitors, such as neomycin and U-73122, which involved a Pertussis toxin-sensitive G-protein. Clone 1D5 and E2 stimulated CK specific activity in human and rat osteoblasts with ten fold higher concentrations than those needed for the membrane effects (0.1 μg/ml and 10 pM, respectively). Both effects were gender-specific since testosterone and 5α-dihydotesterone were uneffective. Tamoxifen and Raloxifene, two estrogen nuclear antagonists, inhibited CK response to 1D5 and E2 and Ca2+ response to 1D5, but not CA2+ response to E2. By contrast, (Fab′)2 dimer, a proteolytic fragment of 1D5 with antagonist properties, inhibited both membrane and genomic effects of 1D5 and E2. In conclusion, these results imply that clone 1D5 has an estrogen like activity both at the membrane and nuclear levels in female human and rat osteoblasts. 1D5 must therefore interact with membrane binding sites, penetrate the cells, and reach the nuclear receptors by an as yet uncharacterized mechanism. J. Cell. Biochem. 65:53-66. © 1997 Wiley-Liss, Inc.
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    Altered cell shape is linked to increased p34cdc2 gene expression in fibroblasts expressing a mutant E2F-1 transcription factor (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 83-94 
    Details
    ISSN: 0730-2312
    Keywords: E2F1 ; E2F1d87 ; NIH3TH ; fibroblasts ; p34cdc2 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The E2F1 transcription factor or an amino terminal deletion mutant termed E2F1d87 was constitutively expressed in NIH3T3 fibroblasts. Cells expressing wild-type E2F1 display a morphology indistinguishable from that of normal fibroblasts. However, the E2F1d87-expressing cells exhibited a distinct rounding during culture in media containing 10% calf serum. The morphology change was most pronounced during S phase, which was considerably lengthened in the E2F1d87-expressing cells. Consistent with this rounded shape, the E2F1d87-expressing cells have significantly increased levels of both p34cdc2 mRNA and protein. Also observed was an increase in active p34cdc2 in immunoprecipitates from extracts of the E2F1d87 cell line, as assayed by histone H1 kinase assay. The upregulation of p34cdc2 expression occurs at the transcriptional level and requires ectopic E2F1d87 along with serum growth factor stimulation, since culture of these cells in low serum media results in a flattened shape and a drop in p34cdc2 expression compared to that of the control cells. J. Cell. Biochem. 65:83-94. © 1997 Wiley-Liss, Inc.
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    Mechanical continuity and reversible chromosome disassembly within intact genomes removed from living cells (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 114-130 
    Details
    ISSN: 0730-2312
    Keywords: chromatin ; histone ; mitosis ; nuclear matrix ; nucleolus ; micromanipulation ; tensegrity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Chromatin is thought to be structurally discontinuous because it is packaged into morphologically distinct chromosomes that appear physically isolated from one another in metaphase preparations used for cytogenetic studies. However, analysis of chromosome positioning and movement suggest that different chromosomes often behave as if they were physically connected in interphase as well as mitosis. To address this paradox directly, we used a microsurgical technique to physically remove nucleoplasm or chromosomes from living cells under isotonic conditions. Using this approach, we found that pulling a single nucleolus or chromosome out from interphase or mitotic cells resulted in sequential removal of the remaining nucleoli and chromosomes, interconnected by a continuous elastic thread. Enzymatic treatments of interphase nucleoplasm and chromosome chains held under tension revealed that mechanical continuity within the chromatin was mediated by elements sensitive to DNase or micrococcal nuclease, but not RNases, formamide at high temperature, or proteases. In contrast, mechanical coupling between mitotic chromosomes and the surrounding cytoplasm appeared to be mediated by gelsolin-sensitive microfilaments. Furthermore, when ion concentations were raised and lowered, both the chromosomes and the interconnecting strands underwent multiple rounds of decondensation and recondensation. As a result of these dynamic structural alterations, the mitotic chains also became sensitive to disruption by restriction enzymes. Ion-induced chromosome decondensation could be blocked by treatment with DNA binding dyes, agents that reduce protein disulfide linkages within nuclear matrix, or an antibody directed against histones. Fully decondensed chromatin strands also could be induced to recondense into chromosomes with pre-existing size, shape, number, and position by adding anti-histone antibodies. Conversely, removal of histones by proteolysis or heparin treatment produced chromosome decondensation which could be reversed by addition of histone H1, but not histones H2b or H3. These data suggest that DNA, its associated protein scaffolds, and surrounding cytoskeletal networks function as a structurally-unified system. Mechanical coupling within the nucleoplasm may coordinate dynamic alterations in chromatin structure, guide chromosome movement, and ensure fidelity of mitosis. J. Cell. Biochem. 65:114-130. © 1997 Wiley-Liss, Inc.
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    Common mechanism for the estrogen agonist and antagonist activities of droloxifene (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 159-171 
    Details
    ISSN: 0730-2312
    Keywords: breast cancer ; droloxifene ; estrogen replacement therapy ; apoptosis ; osteoclasts ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The incidence of postmenopausal osteoporosis is increasing as the population ages. Even though estrogen replacement therapy has proven beneficial in reducing the number of skeletal fractures, the known risks and associated side-effects of estrogen replacement therapy make compliance poor. Recent research has focused on the development of tissue specific estrogen agonist/anatagonists such as droloxifene which can prevent estrogen deficiency-induced bone loss without causing uterine hypertrophy. Furthermore, droloxifene acts as a full estrogen antagonist on breast tissue and is being evaluated for treatment of advanced breast cancer. In this report we propose a common mechanism of action for droloxifene that underlies its estrogen agonist and antagonist effects in different tissues. Droloxifene and estrogen, which have identical effects on bone in vivo, both induced p53 expression and apoptosis in cells of in vitro rat bone marrow cultures resulting in a decrease in the number of bone-resorbing osteoclasts. Droloxifene is growth inhibitory in MCF-7 human breast cancer cells and therefore acts as an antagonist, whereas estrogen is mitogenic to these cells and acts as an agonist. Droloxifene, but not estrogen, induced p53 expression and apoptosis in MCF-7 cells. These results indicate that the induction of apoptosis by droloxifene may be the common mechanism for both its estrogen agonist effects in bone and its antagonist effects in breast tissue. J. Cell. Biochem. 65:159-171. © 1997 Wiley-Liss, Inc.
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    Transforming growth factor-β1 regulation of bone sialoprotein gene transcription: Identification of a TGF-β activation element in the rat BSP gene promoter (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 501-512 
    Details
    ISSN: 0730-2312
    Keywords: bone sialoprotein ; gene regulation ; mineralized tissues ; TGF-β1 ; transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Transforming growth factor-β (TGF-β) increases steady-state mRNA levels of several extracellular matrix proteins in mineralized connective tissues. Bone sialoprotein (BSP) is a major constituent of the bone matrix, thought to initiate and regulate the formation of mineral crystals. To determine the molecular pathways of TGF-β1 regulation of bone proteins, we have analyzed the effects of the TGF-β1 on the expression of the BSP in the rat osteosarcoma cell line (ROS 17/2.8). TGF-β1 at 1 ng/ml, increased BSP mRNA levels in ROS 17/2.8 cells ∼8-fold; the stimulation was first evident at 3 hr, reached maximal levels at 12 hr and slowly declined thereafter. Since the stability of the BSP mRNA was not significantly affected by TGF-β1, and nuclear “run-on” transcription analyses revealed only a ∼2-fold increase in the transcription of the BSP gene, most of the increase in BSP mRNA appeared to involve a nuclear post-transcriptional mechanism. Moreover, the effects of TGF-β1 were indirect, since the increase in BSP mRNA was abrogated by cycloheximide (28 μg/ml). To identify the site of transcriptional regulation by TGF-β1, transient transfection analyses were performed using BSP gene promoter constructs linked to a luciferase reporter gene. Constructs that included nt -801 to -426 of the promoter sequence were found to enhance transcriptional activity ∼1.8-fold in cells treated with TGF-β1. Within this sequence, ∼500 nt upstream of the transcription start site, a putative TGF-β activation element (TAE) was identified that contained the 5′-portion of the nuclearfactor-1 (NF-1) canonical sequence (TTGGC) overlapping a consensus sequence for activator protein-2 (AP-2). The functionality of the TAE was shown by an increased binding of a nuclear protein from TGF-β1 stimulated cells in gel mobility shift assays and from the attenuation of TGF-β1-induced luciferase activity when cells were co-transfected with a double-stranded TAE oligonucleotide. Competition gel mobility shift analyses revealed that the nuclear protein that binds to the TAE has similar properties to, but is distinct from, NF-1 nuclear protein. These studies have therefore identified a TGF-β activation element (TAE) in the rat BSP gene promoter that mediates the stimulatory effects of TGF-β1 on BSP gene transcription. J. Cell. Biochem. 65:501-512. © 1997 Wiley-Liss Inc.
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    Parathyroid hormone uses both adenylate cyclase and protein kinase C to regulate acid production in osteoclasts (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 565-573 
    Details
    ISSN: 0730-2312
    Keywords: calcium-regulating hormones ; bone cells ; acridine orange ; signal transduction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteoclasts, isolated from the endosteum of 2.5- to 3-week-old chickens, were treated with acridine orange, a hydrogen ion concentration-sensitive fluorescent dye, in order to monitor changes in acid production. The adenylate cyclase inhibitor, alloxan, blocked parathyroid hormone (PTH)-stimulated acid production. Dibutyryl cyclic adenosine monophosphate, a membrane-permeant form of cyclic adenosine monophosphate, mimicked the PTH effect. Bisindolylmaleimide, a specific inhibitor of protein kinase C (PKC), blocked the initial stimulation (15, 30, and 60 min) of acid production by PTH but had no effect on long-term stimulation (120 min). Confocal microscopy of osteoclasts stained with fluorescein-conjugated bisindolylmaleimide revealed a shift in location of PKC from the cytoplasm to the plasma membrane region after treatment with parathyroid hormone. The results of these studies support the hypothesis that PTH regulation of acid production in osteoclasts involves both adenylate cyclase and PKC as effectors. J. Cell. Biochem. 65:565-573. © 1997 Wiley-Liss Inc.
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    GA-binding protein is involved in altered expression of ribosomal protein L32 gene (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 287-307 
    Details
    ISSN: 0730-2312
    Keywords: GA-binding protein ; rpL32 gene promoter ; ribosomes ; differentiation/dedifferentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Differentiation of BC3H1 myoblasts to myocytes is accompanied by a 67% drop in the rate of rpL32 gene transcription. Addition of high concentrations of serum to resting myocyte populations stimulates cell growth and subsequent dedifferentiation to proliferating myoblasts with a return to the normal rate of rpL32 gene transcription. During these growth rate changes the binding activities of previously identified factors (β, γ, δ) which interact with the rpL32 gene promoter were examined by mobility shift assays. Binding of the β factor (an Ets related protein) to an oligonucleotide containing the β element was reduced significantly in myocycle nuclear extracts, but subsequent dedifferentiation increased binding within 30 min in either the presence or absence of the cycloheximide. Binding of the γ and δ factors to their respective elements changed only slightly during these processes. Dephosphorylation of either myoblast or myocyte extracts resulted in increased binding of the β factor suggesting that binding activity of the β factor is modulated by phosphorylation during the changes in BC3H1 myoblasts growth rate. In addition, mobility shift assays with recombinant GABP α and β proteins and their specific antibodies revealed that GABP proteins bind to the rpL32 gene promoter in a sequence dependent manner, and that similar proteins are present in BC3H1 myoblast/myocyte extracts. These results support the premise that the GABP heterodimer is the rpL32 β factor. Furthermore, during BC3H1 myoblast differentiation and dedifferentiation neither the levels of the GABP α and β proteins nor their respective mRNAs change. These results suggest that GABP is a constitutively expressed protein and is involved in regulating rpL32 gene by post-transcriptional modifications. J. Cell. Biochem. 65:287-307. © 1997 Wiley-Liss, Inc.
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    Estrogen responsiveness of renal calbindin-D28k gene expression in rat kidney (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 340-348 
    Details
    ISSN: 0730-2312
    Keywords: estrogen ; Calbindin D28k ; rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In women, calcium excretion in the urine rises after menopause and falls with estrogen replacement therapy. The amount of calcium lost in the urine following estrogen therapy is less than should occur based on changes in serum calcium and the amount of calcium filtered by the kidney. This suggests there may be a direct effect of estrogen therapy to increase renal calcium reabsorption. Calbindin D28k is a putative calcium ferry protein located in the distal renal tubules which has been shown to increase transcellular calcium transport. We proposed that estrogen loss after menopause may diminish gene expression of renal calbindin D28k and subsequently diminish renal calcium reabsorption. We used the ovariectomized rat model of estrogen deficiency to investigate changes at the messenger RNA level of calbindin D28k in ovariectomized rats (OVX), sham ovariectomized rats (S-OVX), and estrogen treated ovariectomized rats (E-OVX). We have demonstrated that ovariectomy in rats diminishes the gene expression of renal calbindin D28k. The mRNA levels were approximately three times lower in OVX rats than S-OVX rats. Administration of 17β estradiol to OVX rats produced a significant increase in mRNA level to greater than the S-OVX rats by 4 h. Measurement of serum 1,25 dihydroxyvitamin D3 showed lower level in OVX rats than S-OVX rats but no significant change in E-OVX animals. In conclusion, our results indicate that estrogen increases renal calbindin D28k mRNA levels, by a mechanism independent of changes in 1,25 dihydroxyvitamin D3. This may result in increased expression of calbindin D28k protein which may have a role in reducing renal calcium excretion. J. Cell. Biochem. 65:340-348. © 1997 Wiley-Liss, Inc.
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    Transcriptional and post-transcriptional control of lysyl oxidase expression in vascular smooth muscle cells: Effects of TGF-β1 and serum deprivation (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 395-407 
    Details
    ISSN: 0730-2312
    Keywords: lysyl oxidase ; vascular smooth muscle cells ; mRNA stability ; collagen ; elastin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Transforming growth factor-β1 (TGF-β1) markedly reduced cell proliferation and elevated steady state lysyl oxidase (LO) mRNA 3-fold in neonatal rat aorta smooth muscle cells cultured in medium containing 10% fetal bovine serum. The increase in LO mRNA was prevented by the presence of cycloheximide, indicative of controlling events at the level of protein synthesis. The basal level of mRNA in cells proliferating in 10% fetal bovine serum in the absence of TGF-β1 was enhanced 7-fold upon decreasing growth by shifting to medium containing 0.5% serum. Changes in LO activity paralleled those in LO mRNA. Nuclear run-on assays revealed that the stimulation of expression in 0.5% serum involved increased gene transcription whereas that caused by TGF-β1 was mostly post-transcriptional in origin. LO mRNA was quite labile (t½ approximately 3 h) in 10% serum but was markedly stabilized (t½ 〉 12 h) by the presence of TGF-β1 in the 10% serum medium. LO mRNA was also considerably more stable under retarded growth conditions (0.5% serum) in the absence of TGF-β1. LO promoter activity in luciferase reporter constructs transfected into these cells was low and not significantly affected by the addition of TGF-β1 to the 10% serum medium but was markedly elevated by shifting from 10 to 0.5% serum in the absence of TGF-β1. Thus, LO expression is inversely correlated with cell proliferation, and is subject to control at transcriptional and post-transcriptional levels. TGF-β1 enhances LO expression in these cells by dramatically stabilizing LO mRNA. J. Cell. Biochem. 65:395-407. © 1997 Wiley-Liss, Inc.
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    Genetic and biochemical analysis of the transmembrane domain of Arabidopsis 3-hydroxy-3-methylglutaryl coenzyme A reductase (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 443-459 
    Details
    ISSN: 0730-2312
    Keywords: Arabidosis thaliana ; HMG CoA reductase ; Hmg1p ; transmembrane domain ; protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We have examined the amino terminal membrane anchoring domain of Arabidopsis thaliana 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmg1p), a key enzyme of the isoprenoid biosynthetic pathway. Using both in vitro and in vivo approaches, we have analyzed a series of recombinant derivatives to identify key structural elements which play a role in defining Hmg1p transmembrane topology. Based on our results, we have proposed a topological model for Hmg1p in which the enzyme spans the lipid bilayer twice. We have shown the two transmembrane segments, designated TMS1 and TMS2, to be structurally and functionally inequivalent in their ability to direct the targeting and orientation of reporter proteins. Furthermore, we provide evidence indicating both the extreme amino terminal end and carboxyl terminal domain of the protein reside in the cytosol. This model therefore provides a key basis for the future examination of the role of the transmembrane domain in the targeting and regulation of Hmg1p in plant cells. J. Cell. Biochem. 65:443-459. © 1997 Wiley-Liss Inc.
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    Simultaneous activity of two different mechanisms of folate transport in ovarian carcinoma cell lines (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 479-491 
    Details
    ISSN: 0730-2312
    Keywords: folate receptor ; folate uptake ; reduced folate carrier ; ovarian carcinoma cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We investigated whether the folate receptor α-isoform (FRα), which is overexpressed on ovarian carcinoma cells, is functionally active in internalizing the physiological form of folate, 5-methyl tetrahydrofolate (THF). Six ovarian tumor cell lines, expressing different levels of FRα (COR ≫ OVCAR3 〉 IGROV1 〉 OVCAR4 〉 SKOV3 〉 OVCAR5), were maintained in folate-depleted medium and internalization of 10 nM evaluated as acid-resistant radioactivity at 0° and 37°C. The amount of 5-methyl[3H]THF present in this fraction was not strictly related to the number of membrane receptors, since even cell lines with low FRα expression, e.g., OVCAR4, showed efficient internalization. Time-course studies indicated that, whereas no uptake was detected at 0°C, at 37°C the internalized fraction showed a slow and constant increase, until 4 h. At this time, the internalized radioactivity represented 〈50% of the total bound in COR, OVCAR3 and IGROV1 cells, whereas the other cell lines tested internalized fourfold more folate than their surface binding capacity. The incubation in the presence of a concentration (50 nM) of 5-methyl[3H]THF, which best ensures receptors saturation on cells with highest FR levels (COR and OVCAR3), had slight effect on surface binding of all the tested cell lines, including IGROV1 and SKOV3. In contrast, the increase of the uptake was more pronounced, particularly in SKOV3 cells. These results, together with the accumulation curves of folic acid (FA) and 5-methylTHF at 37°C, suggested the presence of a molecule on ovarian carcinoma cells with high affinity for reduced folates, possibly a reduced folate carrier (RFC). Measurement of radioactivity present in the supernatant of IGROV1 and SKOV3 cells, subjected to hypotonic lysis and cell fractionation, further indicated that 5-methyl[3H]THF was translocated to the cytosol and, despite differences in membrane levels of FRα expression this internalized fraction was similar in both cell lines. Inhibition experiments to selectively block FRα or RFC activity showed a differential sensitivity of the two pathways depending on the cell line examined. Internalization was more consistently inhibited on IGROV1 than on SKOV3 cells by treatments that disrupt FRα activity, e.g., incubation with excess FA and phosphatidylinositol specific phospholipase C, whereas Probenecid, which preferentially inhibits the carrier-mediated pathway, showed a strong inhibitory effect on both cell lines. These findings suggest that the internalization of 5-methylTHF in these tumor cells depends not only on the level of overexpressed FRα, but another transport route, with features characteristic for RFC, is functional and participates in folate uptake. J. Cell. Biochem. 65:479-491. © 1997 Wiley-Liss Inc.
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    Identification of Rad's effector-binding domain, intracellular localization, and analysis of expression in Pima Indians (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 527-541 
    Details
    ISSN: 0730-2312
    Keywords: insulin resistance ; skeletal muscle ; NIDDM ; GTP-binding protein ; thin filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In order to characterize the endogenous gene product for rad (ras-related protein associated with diabetes), we prepared antibodies to synthetic peptides that correspond to amino acids (109-121, 178-195, 254-271) within the protein. These antibodies were used to analyze the expression, structure, and function of rad. Western analysis with these antibodies revealed that rad was a 46 kDa protein which was expressed during myotube formation. Further, immunolocalization studies showed that rad localized to thin filamentous regions in skeletal muscle. Interestingly, when muscle biopsies from diabetic and control Pima Indians were compared, no differences in rad protein or mRNA expression were observed. Similarly, no differences were observed in protein expression in diabetic and control Zucker diabetic fatty (ZDF) rats. Functional analysis of muscle rad revealed that its GTP-binding activity was inhibited by the addition of N-ethylmaliemide, GTP, GTPγS, and GDPβS but not ATP or dithiothreitol. Moreover, cytosol-dependent rad-GTPase activity was stimulated by the peptide corresponding to amino acids 109-121. Antibodies corresponding to this epitope inhibited cytosol-dependent rad-GTPase activity. Taken together, the results indicate that 1) rad is a 46 kDa GTP-binding protein localized to thin filaments in muscle and its expression increases during myoblast fusion, 2) expression of rad in Pima Indians and ZDF rats does not correlate with diabetes, and 3) the amino acids (109-121) may be involved in regulating rad-GTPase activity, perhaps by interacting with a cytosolic factor(s) regulating nucleotide exchange and/or hydrolysis. J. Cell. Biochem. 65:527-541. © 1997 Wiley-Liss Inc.
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    Roles of p300, pocket proteins, and hTBP in E1A-mediated transcriptional regulation and inhibition of p53 transactivation activity (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 277-285 
    Details
    ISSN: 0730-2312
    Keywords: pRb ; p107 ; p130/Rb2 ; TBP ; transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The conserved region 1 and the extreme N-terminus of adenoviral oncoprotein E1A are essential for transforming activity. They also play roles in the interaction of E1A with p300/CBP and pRb and are involved in both transactivation and repression of host gene expression. It was reported recently that p53-mediated transactivation is specifically repressed by E1A and that p53-induced apoptosis can be protected by pRb. In this report, we investigated the roles of pRb and p300 in the N-terminus of E1A-mediated transcriptional regulation. We demonstrate here that p300 and pRb have no effect on DBD.1-70 transactivation and that overexpression of p300 or pRb failed to relieve the repression by E1A. Repression of p53 transactivation requires both the extreme amino terminus and CR1 but not CR2. This repressive activity of E1A specifically correlates with E1A's ability to bind p300 and TBP. On the other hand, E1A inhibited the transactivation activity of a fusion construct containing the DNA binding domain of yeast Gal4 and the transactivation domain of p53. When p53 was cotransfected with E1A, similar inhibition was found in Saos-2 cells that lack endogenous pRb and p53 activity. Introduction of pRb into Saos-2 cells did not affect p53 transcription activity. E1A-mediated repression can be relieved by overexpression of either p300, hTBP, or TFIIB but cannot be released by overexpression of pocket proteins. Our data suggest that p300/CBP and TBP but not the pocket proteins, pRb, p107, and pRb2/p130 are functional targets of E1A in transcriptional regulation and that p53 transactivation requires the function of the p300/TBP/TFIIB complex, thus delineating a new pathway by which E1A may exert its transforming activity. J. Cell. Biochem. 66:277-285, 1997. © 1997 Wiley-Liss, Inc.
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    Cell-type specific regulation of human interstitial collagenase-1 gene expression by interleukin-1β (IL-1β) in human fibroblasts and BC-8701 breast cancer cells (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 322-336 
    Details
    ISSN: 0730-2312
    Keywords: transcription ; promoter ; mRNA stability ; nucleic acid sequence ; matrix metalloproteinase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Interleukin-1β (IL-1β) is a potent cytokine that stimulates interstitial collagenase-1 (matrix metalloproteinase-1; MMP-1). In this study, we compared the mechanism(s) by which IL-1β induces collagenase gene expression in two very different cells, normal human foreskin fibroblasts (HFFs) and an aggressive breast cancer cell line, BC-8701 cells. Northern analysis showed that the time course of collagenase induction was distinct in the two cells: although both cells expressed low levels of MMP-1 constitutively, addition of IL-1β increased MMP-1 mRNA in HFFs by 1 h and levels remained high over a 24-h period. In contrast, MMP-1 levels in IL-1β-treated BC-8701 cells did not increase until 4 h, peaked by 12 h and then declined. To analyze the transcriptional response, we cloned and sequenced more than 4,300 bp of the human MMP-1 promoter, and from this promoter clone, we prepared a series of 5′-deletion constructs linked to the luciferase reporter and transiently transfected these constructs into both cell types to measure both basal and IL-1β induced transcription. When both cell types were uninduced, promoter fragments containing less than 2,900 bp gave only a minimal transcriptional response, while larger fragments showed increased transcriptional activity. With IL-1β treatment, significant responsiveness (P 〈 0.001) in HFFs was seen only with the larger fragments, while in the BC-8701 cells, all fragments were significantly induced with IL-1β. Finally, we found that IL-1β stabilized MMP-1 mRNA in normal fibroblasts, but not in BC-8701 breast cancer cells. We conclude that both the transcriptional and post-transcriptional regulation of MMP-1 gene expression by IL-1β is controlled by cell-type specific mechanisms, and we suggest that IL-1 induced MMP-1 expression in tumor cells and in neighboring stromal cells may amplify the invasive ability of tumor cells. J. Cell. Biochem. 66:322-336, 1977. © 1997 Wiley-Liss, Inc.
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    CBP70, a glycosylated nuclear lectin (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 370-385 
    Details
    ISSN: 0730-2312
    Keywords: nucleus ; glycoprotein ; lectin ; HL60 ; affinity chromatography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Some years ago, a lectin designated CBP70 that recognized glucose (Glc) but had a stronger affinity for N-acetylglucosamine (GlcNAc), was first isolated from HL60 cell nuclei. Recently, a cytoplasmic form of this lectin was described, and one 82 kDa nuclear ligand was characterized for the nuclear CBP70. In the present study, the use of Pronase digestion and the trifluoromethanesulphonic acid (TFMS) procedure strongly suggest that the nuclear and the cytoplasmic CBP70 have a same 23 kDa polypeptide backbone and, consequently, could be the same protein. In order to know the protein better and to obtain the best recombinant possible in the future, the post-translational modification of the nuclear and cytoplasmic CBP70 was analyzed in terms of glycosylation. Severals lines of evidence indicate that both forms of CBP70 are N- and O-glycosylated. Surprisingly, this glycosylation pattern differs between the two forms, as revealed by β-elimination, hydrazinolysis, peptide-N-glycosydase F (PNGase F), and TFMS reactions. The two preparations were analyzed by affinity chromatography on immobilized lectins [Ricinus communis-I agglutinin (RCA-I), Arachis hypogaea agglutinin (PNA), Galanthus nivalis agglutinin (GNA), and wheat germ agglutinin (WGA)] and by lectin-blotting analysis [Sambucus nigra agglutinin (SNA), Maackia amurensis agglutinin (MAA), Lotus tetragonolobus (Lotus), succinylated-WGA, and Psathyrella velutina agglutinin (PVA)]. Both forms of CBP70 have the following sugar moities: terminal βGal residues, Galβ1-3 GalNAc, Man α1-3 Man, sialic acid α2-6 linked to Gal or GalNAc; and sialic acid α2-3 linked to Gal. However, only nuclear CBP70 have terminal GlcNAc and α-L-fucose residues.All these data are consistent with the fact that different glycosylation pattern found for each form of CBP70 might act as a complementary signal for cellular targeting. J. Cell. Biochem. 66:370-385, 1997. © 1997 Wiley-Liss, Inc.
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    Vitamin D3 analogs and their 24-Oxo metabolites equally inhibit clonal proliferation of a variety of cancer cells but have differing molecular effects (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 413-425 
    Details
    ISSN: 0730-2312
    Keywords: vitamin D3 analogs ; 24-oxo metabolites ; growth inhibition ; differentiation ; apoptosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The seco-steroid hormone, 1α,25 dihydroxyvitamin D3 (1α,25(OH)2D3) binds to a specific nuclear receptor that acts as a ligand-inducible transcription factor. The resulting genomic effects include partial arrest in G0/G1 of the cell cycle and induction of differentiation; these effects have been observed in various types of cancer. Recently, we produced enzymatically the natural 24-oxo metabolites of 1α,25(OH)2D3 and two of its potent synthetic analogs (1α,25-(OH)2-16-ene-D3 and 1α,25-(OH)2-20-epi-D3) using a rat kidney perfusion system. We have found that the 24-oxo metabolites of both 1α,25(OH)2D3 and its analogs have either the same or greater antiproliferative activity against various cancer cells as their parental compounds. Notably, two cell lines (DU-145 (prostate cancer) and MDA-MB-436 [breast cancer]) that were extremely resistant to the antiproliferative effects of vitamin D3 analogs displayed greater sensitivity towards the 24-oxo metabolite of the vitamin D3 analog. Similarly, the 24-oxo metabolites had the capacity to induce differentiation and apoptosis and to diminish the proportion of cells in S phase. Most interestingly, while the analog 1α,25(OH)2-20-epi-D3 induced expression of BRCA1 in MCF-7 breast cancer cells; its 24-oxo metabolite dramatically suppressed BRAC1 expression. Thus, we have shown for the first time that the various biological activities produced by the hormone 1α,25(OH)2D3 and some of its analogs may represent a combination of actions by the hormone 1α,25(OH)2D3 and its natural 24-oxo metabolites. J. Cell. Biochem. 66:413-425, 1997. © 1997 Wiley-Liss, Inc.
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    Combination of osteoinductive bone proteins differentiates mesenchymal C3H/10T1/2 cells specifically to the cartilage lineage (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 325-339 
    Details
    ISSN: 0730-2312
    Keywords: bone morphogenetic protein ; defined media ; in vitro ; development ; stem cell ; ascorbic acid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: During embryonic development, cartilage formation involves the condensation of mesenchymal stem cells and a series of maturation steps that ultimately results in the mineralized hypertrophic chondrocyte. The embryonic, murine, mesenchymal stem cell line, C3H/10T1/2, is pluripotent; exposure to azacytidine or to bone morphogenetic protein-2 or -4 results in low rates of differentiation to three mesengenic lineages. In contrast to previous studies, we report conditions for 10T1/2 differentiation specifically to the cartilage lineage and at high yields. These conditions include high cell density micromass cultures, a purified mixture of osteoinductive proteins (BP; Intermedics Orthopedics, Denver, CO), a serum substitute, 50 μg/ml ascorbic acid, and 10 mM β-glycerophosphate. The cartilagenous fate was confirmed by 1) histological detection of sulfated proteoglycans, 2) electron microscopic detection of proteoglycan and rounded cells separated by extracellular matrix containing short, disorganized collagen fibrils, 3) morphological detection of a chondrocytes surrounded by a territorial matrix and encompassed within a distinct perichondrium, and 4) immunocytochemical detection of type II collagen and link protein. After 4 weeks in culture, mature although unmineralized cartilage was observed, as indicated by hypertrophic morphology, immunocytochemical detection of osteocalcin, and histological detection of lacunae. These conditions promote overt chondrogenesis for most of the treated cells and preclude lineage determination to the fat, muscle, and bone lineages, as assayed by electron microscopy and histomorphology. The faithful recapitulation of cartilage differentiation that we have established in vitro provides a versatile alternative to the use of chondrocyte and limb bud explant cultures. We propose this as a model system to study the factors that regulate commitment to the chondrogenic lineage, exclusion to related mesengenic pathways, and maturation during chondrogenesis. J. Cell. Biochem. 65:325-339. © 1997 Wiley-Liss, Inc.
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    Vasculogenesis and angiogenesis: Extracellular matrix remodeling in coronary collateral arteries and the ischemic heart (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 388-394 
    Details
    ISSN: 0730-2312
    Keywords: angiogenesis ; vasculogenesis ; collateral ; vessel ; development ; occlusion ; extracellular matrix ; collagenase ; collagen ; heart failure ; matrix metalloproteinase ; tissue inhibitor of metalloproteinase ; growth factors ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Heart failure secondary to ischemic cardiomyopathy is the primary cause of cardiovascular mortality. The promise of the collateral circulation lies in its potential to alter the course of the natural history of coronary heart disease. The collateral circulation of the heart is responsible for supplying blood and oxygen to the myocardium at ischemic risk following severe stenosis and reduced vasoelasticity function of a major coronary artery. In response to flow, stress, and pressure, collateral vessels are restructured and remodeled. Vascular remodeling by its very nature implies synthesis and degradation of extracellular matrix components in the vessel wall. Under normal physiological conditions proteinases that break down the specialized matrix are tightly regulated by antiproteinases. The balance between proteinase and antiproteinase influences is discoordinated during collateral development which leads to adaptive changes in the structure, function, and regulation of extracellular matrix components in the vessel wall. The role of extracellular matrix components in coronary collateral vessel formation in a canine model of chronic coronary artery occlusion has been demonstrated. The role of matrix proteinases and antiproteinases in the collateral vessel play a significant role in the underlying mechanisms of collateral development. This review presents new and significant information regarding the role of extracellular matrix proteinases and antiproteinases in vascular remodeling, function, and collateral development. Such information will have a significant impact on the understanding of the basic biology of the vascular extracellular matrix turnover, remodeling, and function as well as on elucidating potential avenues for pharmacological approaches designed to increase collateral formation and optimize myocardial blood flow in the treatment of ischemic heart disease. J. Cell. Biochem. 65:388-394. © 1997 Wiley-Liss, Inc.
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    Inhibition of cerebellar nitric oxide synthase and cyclic GMP production by melatonin via complex formation with calmodulin (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 430-442 
    Details
    ISSN: 0730-2312
    Keywords: melatonin ; pineal gland ; cerebellum ; nitric oxide ; nitric oxide synthase ; calmodulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Constitutive rat cerebellar nitric oxide synthase (NOS) activity is shown to be inhibited by physiological concentrations of the pineal hormone melatonin. The inhibition was dose-dependent and was coupled to an inhibition of the cyclic GMP production activated by L-arginine. Results also show that calmodulin appears to be involved in this process because its presence in the incubation medium was able to prevent the effect of melatonin on both NOS activity and cyclic GMP production. Moreover, polyacrylamide gel electrophoresis studies suggest that melatonin can interact with calmodulin modifying the binding of the peptide to the synthetic NOS peptide encompassing the calmodulin-binding domain of constitutive NOS from rat cerebellum, the natural mechanism by which calmodulin activates cerebellar NOS. J. Cell. Biochem. 65:430-442. © 1997 Wiley-Liss, Inc.
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    Autoregulation of actin synthesis responds to monomeric actin levels (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 469-478 
    Details
    ISSN: 0730-2312
    Keywords: actin autoregulation ; swinholide A ; dimeric actin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Regulation of the assembly and expression of actin is of major importance in diverse cellular functions such as motility and adhesion and in defining cellular and tissue architecture. These biological processes are controlled by changing the balance between polymerized (F) and soluble (G) actin. Previous studies have indicated the existence of an autoregulatory pathway that links the state of assembly and expression of actin, resulting in the reduction of actin synthesis after actin filaments are depolymerized. We have employed the marine toxins swinholide A and latrunculin A, both disrupting the organization of the actin-cytoskeleton, to determine whether this autoregulatory response is activated by a decrease in the level of polymerized actin or by an increase in monomeric actin concentrations in the cell. We showed that in cells treated with swinholide A the level of filamentous actin is decreased, and using a reversible cross-linking reagent, we found that actin dimers are formed. Latrunculin A also disassembled actin filaments, but produced monomeric actin, followed by a reduction in actin and vinculin expression, while swinholide A treatment elevated the synthesis of these proteins. In cells treated with both latrunculin A and swinholide A, dimeric actin was formed, and actin and vinculin synthesis were higher than in control cells. These results suggest that the substrate that confers an autoregulated reduction in actin expression is monomeric actin, and when its level is decreased by dimeric actin formation, actin synthesis is increased. J. Cell. Biochem. 65:469-478. © 1997 Wiley-Liss Inc.
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    Reduced drug accumulation and multidrug resistance in human breast cancer cells without associated P-glycoprotein or MRP overexpression (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 513-526 
    Details
    ISSN: 0730-2312
    Keywords: mitoxantrone ; drug resistance ; non-Pgp MDR ; rhodamine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: MCF-7 human breast cancer cells selected in Adriamycin in the presence of verapamil developed a multidrug resistant phenotype, which was characterized by as much as 100,000-fold resistance to mitoxantrone, 667-fold resistance to daunorubicin, and 600-fold resistance to doxorubicin. Immunoblot and PCR analyses demonstrated no increase in MDR-1 or MRP expression in resistant cells, relative to parental cells. This phenotype is similar to one previously described in mitoxantrone-selected cells. The cells, designated MCF-7 AdVp, displayed a slower growth rate without alteration in topoisomerase IIα level or activity. Increased efflux and reduced accumulation of daunomycin and rhodamine were observed when compared to parental cells. Depletion of ATP resulted in complete abrogation of efflux of both daunomycin and rhodamine. No apparent alterations in subcellular daunorubicin distribution were observed by confocal microscopy. No differences were noted in intracellular pH. Molecular cloning studies using DNA differential display identified increased expression of the alpha subunit of the amiloride-sensitive sodium channel in resistant cells. Quantitative PCR studies demonstrated an eightfold overexpression of the alpha subunit of the Na+ channel in the resistant subline. This channel may be linked to the mechanism of drug resistance in the AdVp cells. The results presented here support the hypothesis that a novel energy-dependent protein is responsible for the efflux in the AdVp cells. Further identification awaits molecular cloning studies. J. Cell. Biochem. 65:513-526. © 1997 Wiley-Liss Inc.
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    Partial isolation from intact cells of a cell surface-exposed lysophosphatidylinositol-phospholipase C (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 65 (1997), S. 550-564 
    Details
    ISSN: 0730-2312
    Keywords: ecto-PLC ; ecto-enzyme ; phosphoinositide-specific phospholipase C ; cell surface enzyme ; lyso-PI-cleaving PLC ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A novel cell surface phosphoinositide-cleaving phospholipase C (ecto-PLC) activity was isolated from cultured cells by exploiting its presumed external exposure. Biotinylation of intact cells followed by solubilization of the biotinylated proteins from a membrane fraction and recovery onto immobilized-avidin beads, allowed assay of this cell surface enzyme activity apart from the background of the substantial family of intracellular PLCs. Several cell lines of differing ecto-PLC expression were examined as well as cells stably transfected to overexpress the glycosylphosphatidylinositol (GPI)-anchored protein human placental alkaline phosphatase (PLAP) as a cell surface enzyme marker. The resulting bead preparations from ecto-PLC positive cells possessed calcium-dependent PLC activity with preference for lysophosphatidylinositol (lysoPI) rather than phosphatidylinositol (PI). The function of ecto-PLC of intact cells evidently is not to release GPI-anchored proteins at the cell surface, as no detectable Ca2+-dependent release of overexpressed PLAP from ecto-PLC-positive cells was observed. To investigate the cell surface linkage of the ecto-PLC itself, intact cells were treated with bacterial PI-PLC to cleave simple GPI anchors, but no decrease in ecto-PLC activity was observed. High ionic strength washes of biotinylated membranes prior to the generation of bead preparations did not substantially reduce the lysoPI-PLC activity. The results verify that the ecto-PLC is truly cell surface-exposed, and unlike other members of the PLC family that are thought to be peripheral membrane proteins, this novel lysoPI-PLC is most likely a true membrane protein. J. Cell. Biochem. 65:550-564. © 1997 Wiley-Liss Inc.
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    Regulation of adenylyl cyclase isoforms by N-alkanols (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 450-456 
    Details
    ISSN: 0730-2312
    Keywords: type II adenylyl cyclase ; type V adenylyl cyclase ; insect cells ; Gsα ; solubilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We examined the effect of n-alkanols on adenylyl cyclase isoforms (types II and V) overexpressed in insect cells. Ethanol stimulated the type II isoform but not the type V isoform. Ethanol stimulated type II adenylyl cyclase greater than GTPγS, and the treatment of the membrane with GDPβS or cholera toxin did not affect this stimulation. Other n-alkanols inhibited type V adenylyl cyclase activity in proportion to their lipophilic potency. In contrast, type II adenylyl cyclase was stimulated by weakly lipophilic n-alkanols and inhibited by strongly lipophilic n-alkanols. When solubilized membranes and purified preparations were used, all the n-alkanols inhibited type II adenylyl cyclase. Our data suggest that n-alkanols regulated adenylyl cyclase isoform-dependently. Stimulation of the type II isoform was independent from the interaction with Gsα but required the presence of an intact membrane structure. Our study may provide another step to understanding how membrane protein subtypes are differentially regulated by n-alkanols. J. Cell. Biochem. 66:450-456, 1997. © 1997 Wiley-Liss, Inc.
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    Substance P stimulates vascular endothelial cellular reducing capacity in the presence of insulin and human plasma factors (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 471-481 
    Details
    ISSN: 0730-2312
    Keywords: substance P ; cell cycle ; cell growth ; endothelial cell ; tachykinin ; nitric oxide ; insulin ; plasma ; MTT ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Substance P (SP) is an important tachykinin in vascular wall biology. In previous studies [Villablanca et al. (1994): Circ Res 75:1113-1120], the authors have demonstrated that SP is a stimulus for endothelial cell growth and proliferation in serum-free culture conditions with cells quiescent in the G0-G1 phase of the cell cycle. As mitogenic and metabolic activity may interrelate, the purpose of this study was to determine the effects of the vasoactive perivascular neuropeptide SP on changes in the metabolic function of endothelial cells, and to characterize the response, by studying cellular reducing capacity in aortic vascular endothelial cells. In addition, interactions between SP and other growth factors (insulin and non-platelet plasma factors) were investigated and compared to the responses to SP alone. Metabolic effects were determined by evaluating cellular reducing capacity by the conversion of (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) to formazan (the MTT assay). The findings demonstrated that SP alone (10 pg/ml-25 μg/ml) inhibited cellular reducing capacity in vascular endothelial cells. In contrast, SP in the presence of insulin (10 μg/ml) stimulated endothelial reducing capacity, as compared to SP alone, by twofold on average. The effect of SP and insulin was additive at ≤0.001 μg/ml SP, and synergistic at SP concentrations ranging within 0.01-1.0 μg/ml. SP in the presence of human platelet-poor plasma (HPPP, 5%) stimulated endothelial reducing capacity, as compared to SP alone, by threefold on average. The effect of SP and HPPP was additive at ≤0.01 μg/ml SP and synergistic at SP concentrations of 0.1-25 μg/ml. Lastly, SP in the presence of insulin and HPPP stimulated endothelial metabolic activity, as compared to SP alone, by 14-fold on average. An additive response to SP, insulin, and HPPP was observed at the lowest SP concentration studied (10 pg/ml). At all other SP concentrations studied (0.0001-25 μg/ml), the responses to insulin, HPPP, and SP were synergistic. Our studies indicate that the vasoactive neuropeptide substance P may synergize with insulin and HPPP in regulating endothelial cell metabolism. In addition, our findings suggest that the mechanisms by which SP stimulates cellular metabolism are different from the mechanisms by which it stimulates cell growth. J. Cell. Biochem. 66:471-481, 1997. © 1997 Wiley-Liss, Inc.
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    Intracellular distribution of heat-induced stress glycoproteins (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 98-111 
    Details
    ISSN: 0730-2312
    Keywords: hyperthermia ; thermotolerance ; protein glycosylation ; subcellular distribution ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Cellular heat stress results in elevated heat-shock protein (HSP) synthesis and in thermotolerance development. Recently, we demonstrated that protein glycosylation is also an integral part of the stress response with the identification of two major stress glycoproteins, GP50, associated with thermotolerance, and P-SG67, the “prompt” stress glycoprotein induced immediately during acute heat stress. In the present study, we characterized the subcellular location and redistribution of these proteins during the cellular injury and recovery phase. In unheated and heated CHO cells, both stress glycoproteins were present in each subcellular fraction isolated by differential centrifugation. However, the subcellular redistribution in the course of cellular recovery after heat stress was specific for each stress glycoprotein. GP50 was present in all subcellular fractions before heat stress, but showed relatively little redistribution after heat stress. By 24 h of recovery following stress, GP50 showed partial depletion from lysosomes and microsomes, and was mainly present in the mitochondria. Glycosylated P-SG67 was redistributed in a more complex fashion. It was seen predominantly in the lysosomes and microsomes immediately following heat-stress, but after 6 h of recovery following heat stress, it largely disappeared from the microsomes and was present mainly in the cytosol. By 24 h of recovery following heat stress, it was found predominantly in the nucleus-rich fraction and mitochondria. The localization of GP50 and P-SG67 by subcellular fractionation is consistent with immunolocalization studies and contrasts with the translocation of HSP70 after heat stress from cytosol to nuclei and nucleoli. These results reflect a characteristic distribution for each stress glycoprotein; their presence in virtually all subcellular fractions suggests multifunctional roles for the various stress glycoproteins in the cellular heat stress response. J. Cell. Biochem. 66:98-111, 1997. © 1997 Wiley-Liss, Inc.
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    Partial purification of HLAMP-1 provides direct evidence for the multicomponent nature of the particulate matrix associated with cardiac mesenchyme formation (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 112-122 
    Details
    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: H-LAMP-1 is a 283 kDa protein that is involved in the transformation of endothelial cells into mesenchyme within the AV canal and proximal outflow tract of the heart. This protein is part of the particulate matrix that has been suggested to be composed of multicomponent complexes that have been termed cardiac adherons. However, to date no direct evidence has been provided that these proteins are complexed into an adheron-like particle. This report provides the first such evidence by showing that purification of hLAMP-1, under gentle conditions, results in the isolation of multiple bands of similar molecular weight within the fractions that contain anti-hLAMP-1 activity. J. Cell. Biochem. 66:112-122, 1997. © 1997 Wiley-Liss, Inc.
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    Post-proliferative cyclin E-associated kinase activity in differentiated osteoblasts: Inhibition by proliferating osteoblasts and osteosarcoma cells (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 66 (1997), S. 141-152 
    Details
    ISSN: 0730-2312
    Keywords: differentiation ; osteoblasts ; cyclin E-associated kinase ; cyclin dependent kinase inhibitors ; RB related proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Spontaneous differentiation of normal diploid osteoblasts in culture is accompanied by increased cyclin E associated kinase activity on (1) the retinoblastoma susceptibility protein pRB, (2) the p107 RB related protein, and (3) two endogenous cyclin E-associated substrates of 78 and 105 kD. Activity of the differentiation-related cyclin E complexes (diff.ECx) is not recovered in cdc2 or cdk2 immunoprecipitates. Phosphorylation of both the 105 kD endogenous substrate and the p107 exogenous substrate is sensitive to inhibitory activity (diff.ECx-i) present in proliferating osteoblasts. This inhibitory activity is readily recruited by the cyclin E complexes of differentiated osteoblasts but is not found in cyclin E immunoprecipitates of the proliferating cells themselves. Strong inhibitory activity on diff.ECx kinase activity is excerted by proliferating ROS 17/2.8 osteosarcoma cells. However, unlike the normal diploid cells, the diff.ECx-i activity of proliferating ROS 17/2.8 cells is recovered by cyclin E immunoprecipitation. The cyclin-dependent kinase inhibitor p21CIP1/WAF1 inhibits diff.ECx kinase activity. Thus, our results suggest the existence of a unique regulatory system, possibly involving p21CIP1/WAF1, in which inhibitory activity residing in proliferating cells is preferentially targeted towards differentiation-related cyclin E-associated kinase activity. J. Cell. Biochem. 66:141-152, 1997. © 1997 Wiley-Liss, Inc.
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    Analysis of the phosphorylation of human heat shock transcription factor-1 by MAP kinase family members (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 43-54 
    Details
    ISSN: 0730-2312
    Keywords: HSF-1 ; heat shock ; ERK1, phosphorylation ; MAP kinases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The activation of heat shock transcription factor-1 (HSF-1) after treatment of mammalian cells with stresses such as heat shock, heavy metals, or ethanol induces the synthesis of heat shock proteins. HSF-1 is phosphorylated at normal growth temperature and is hyperphosphorylated upon stress. We recently presented evidence that HSF-1 can be phosphorylated by the mitogen activated protein kinase, ERK1, and that such phosphorylation appears to negatively regulate the activity of HSF-1. In this report, we have tested the ability of ERK1 to phosphorylate various HSF-1 deletion mutants. Our results show that ERK1 phosphorylation is dependent on a region of HSF-1 extending from amino acids 280 to 308. This region contains three serine residues that are potential ERK1 phosphorylation sites. The region falls within a previously defined regulatory domain of HSF-1. The possibility of protein kinases other than ERK1 phosphorylating HSF-1 was also examined using in-gel kinase assays. The results show that HSF-1 can be phosphorylated in a ras-dependent manner by other members of the MAP kinase family such as JNK and p38 protein kinases and possibly others. J. Cell. Biochem. 67:43-54, 1997. © 1997 Wiley-Liss, Inc.
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    Decorin inhibits cell attachment to thrombospondin-1 by binding to a KKTR-dependent cell adhesive site present within the N-terminal domain of thrombospondin-1 (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 75-83 
    Details
    ISSN: 0730-2312
    Keywords: decorin ; thrombospondin-1 ; cell attachment ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Skin decorin (DCN) is an antiadhesive dermatan sulfate-rich proteoglycan that interacts with thrombospondin-1 (TSP) and inhibits fibroblast adhesion to TSP [Winnemöller et al., 1992]. Molecular mechanisms by which DCN interacts with TSP and inhibits cell adhesion to TSP are unknown. In the present study, we showed that skin DCN and bone DCN (chondroitin sulfate-rich proteoglycan) were quantitatively identical with respect to their ability to interact with TSP. Using a series of fusion proteins corresponding to the different structural domains of TSP, binding of [125I]DCN to TSP was found to be dependent of the N-terminal domain and, to a lesser extent, of the type 1 repeats and the C-terminal domain of TSP. In addition, heparan sulfate drastically inhibited [125I]DCN binding to solid-phase adsorbed TSP (80% inhibition), suggesting that DCN could bind to the N-terminal domain of TSP through interaction with heparin-binding sequences. To address this question, a series of synthetic peptides, overlapping heparin-binding sequences ARKGSGRR (residues 22-29), KKTR (residues 80-83) and RLRIAKGGVNDN (residues 178-189), were synthesized and tested for their ability to interact with DCN. [125I]DCN interacted only with peptides VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS containing the heparin-binding consensus sequence KKTR. These peptides contained glycosaminoglycan-dependent and -independent binding sites because [125I]DCN binding to VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS was partially reduced upon removal of the glycosaminoglycan chain (65% and 46% inhibition, respectively). [125I]DCN poorly bound to subpeptide MKKTRG and did not bind at all to subpeptides VDAVRTEKGFLLLASLRQ and TLLALERKDHS, suggesting that heparin-binding sequence MKKTRG constituted a DCN binding site when flanked with peptides VDAVRTEKGFLLLASLRQ and TLLALERKDHS. The sequence VDAVRTEKGFLLLASLRQMKKTRGTLLALERKDHS constitutes a cell adhesive active site in the N-terminal domain of TSP [Clezardin et al., 1997], and DCN inhibited the attachment of fibroblastic and osteoblastic cells to peptides VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS by about 50 and 80%, respectively. Although fibroblastic cells also attached to type 3 repeats and the C-terminal domain of TSP, DCN only inhibited cell attachment to the C-terminal domain. Overall, these data indicate that modulation by steric exclusion of cell adhesion to a KKTR-dependent cell adhesive site present within the N-terminal domain of TSP could explain the antiadhesive properties of DCN. J. Cell. Biochem. 67:75-83, 1997. © 1997 Wiley-Liss, Inc.
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    Increases in mRNA levels of glucose transporters types 1 and 3 in Ehrlich ascites tumor cells during tumor development (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 131-135 
    Details
    ISSN: 0730-2312
    Keywords: Ehrlich ascites tumor ; glucose transporter ; mRNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A common feature of many tumors is an increase in glucose catabolism during tumor growth. We studied the mechanism of this phenomenon by using Ehrlich ascites tumor bearing mice as the animal model. We found that Ehrlich ascites tumor cells possess only glucose transporter 1 (GLUT1) and GLUT3 but no GLUT2, GLUT4, or GLUT5. The mRNA levels of GLUT1 and GLUT3 increased progressively in the tumour during development; however, there were no changes observable in mRNA levels of glucose transporters of all types in brain, liver, and heart of the host mice. These findings suggest that Ehrlich ascites tumor augments its glucose transport mechanism relative to other tissues in response to its unique growth needs. J. Cell. Biochem. 67:131-135, 1997. © 1997 Wiley-Liss, Inc.
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    Prolidase activity in fibroblasts is regulated by interaction of extracellular matrix with cell surface integrin receptors This article is a US Government work and, as such, is in the public domain in the United States of America. (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 166-175 
    Details
    ISSN: 0730-2312
    Keywords: prolidase ; fibroblasts ; collagen ; integrins ; extracellular matrix-cell interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Prolidase (EC 3.4.13.9) is a ubiquitously distributed imidodipeptidase that catalyzes the hydrolysis of C-terminal proline or hydroxyproline containing dipeptides. The enzyme plays an important role in the recycling of proline for collagen synthesis and cell growth. An increase in enzyme activity is correlated with increased rates of collagen turnover indicative of extracellular matrix (ECM) remodeling, but the mechanism linking prolidase activity and ECM is poorly understood. Thus, the effect of ECM-cell interaction on intracellular prolidase activity is of special interest. In cultured human skin fibroblasts, the interaction with ECM and, more specifically, type I collagen mediated by the β1 integrin receptor regulates cellular prolidase activity. Supporting evidence comes from the following observations: 1) in sparse cells with a low amount of ECM collagen or in confluent cells in which ECM collagen was removed by collagenase (but not by trypsin or elastase) treatment, prolidase activity was decreased; 2) this effect was reversed by the addition of type I collagen or β1 integrin antibody (agonist for β1 integrin receptor); 3) sparse cells (with typically low prolidase activity) showed increased prolidase activity when grown on plates coated with type I collagen or on type IV collagen and laminin, constituents of basement membrane; 4) the relative differences in prolidase activity due to collagenase treatment and subsequent recovery of the activity by β1 integrin antibody or type I collagen treatment were accompanied by parallel differences in the amount of the enzyme protein recovered from these cells, as shown by Western immunoblot analysis. Thus, we conclude that prolidase activity responded to ECM metabolism (tissue remodeling) through signals mediated by the integrin receptor. J. Cell. Biochem. 67:166-175, 1997. Published 1997 Wiley-Liss, Inc.
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    Detection and cloning of epidermal zinc-α2-glycoprotein cDNA and expression in normal human skin and in tumors (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 216-222 
    Details
    ISSN: 0730-2312
    Keywords: stratified epithelia ; carcinomas ; cell differentiation ; gene expression ; keratinocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Zinc-α2-glycoprotein (Znα2gp) is almost ubiquitous in body fluids, and its antibody labels the corresponding secretory epithelia. We have found that Znα2gp is also expressed in human epidermis. We cloned the Znα2gp cDNA by screening our cDNA library, derived from epidermal keratinocytes, with a probe for prostate Znα2gp. It had complete nucleic acid sequence homology with that from prostate, including the signal peptide. Just as Znα2gp expression is higher in more differentiated breast tumors, so in skin tumors the highest mRNA levels occurred in the normal controls, the lowest in basal cell carcinomas (the least differentiated epidermal tumor type), and intermediate levels in squamous cell carcinomas and Merkel cell carcinomas. A similar increase in Znα2gp gene expression with differentiation was observed when epidermal keratinocytes were cultured in media that varied in cellular maturation potential. J. Cell. Biochem. 67:216-222, 1997. © 1997 Wiley-Liss, Inc.
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    Purification and characterization of a silica-induced bronchoalveolar lavage protein with fibroblast growth-promoting activity (1997)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 257-264 
    Details
    ISSN: 0730-2312
    Keywords: silicosis ; bronchoalveolar lavage protein ; fibroblast proliferation-promoting factor ; inducible macrophage factor ; fibrosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Experimentally induced silicosis provides a good model for chronic interstitial pulmonary inflammation and fibrosis. In the present study, a specific single polypeptide with an apparent molecular mass of 58,000 and a pI of 4.5 was purified and characterized from the bronchoalveolar lavage fluid of silicotic rats. The same protein was also isolated from both the extract and conditioned medium of alveolar macrophages of silicotic rats. Therefore, this protein was termed an inducible silicotic (rat) bronchoalveolar lavage protein-p58 (iSBLP58) or an inducible silicotic (rat) pulmonary macrophage factor (iSPMF-p58). iSBLP58 has been purified to homogeneity by a combination of gel permeation, Mono Q ion exchange, and reverse-phase high performance liquid chromatography. This polypeptide displayed a potent fibroblast growth-promoting activity in vitro. The sequence of the first 15 NH2-terminal amino acids was determined and was found to have high sequence homology with members of the mammalian chitinase-like protein family, which includes human cartilage gp39, mammalian oviduct-specific glycoprotein, and a secretory protein from activated mouse macrophages. J. Cell. Biochem. 67:257-264, 1997. © 1997 Wiley-Liss, Inc.
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