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  • General Chemistry  (38)
  • Analytical Chemistry and Spectroscopy  (10)
  • oligomers
  • Wiley-Blackwell  (49)
  • 1995-1999  (36)
  • 1980-1984  (13)
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  • Wiley-Blackwell  (49)
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  • 1
    Electronic Resource
    Electronic Resource
    Separation of Positional Isomers on A, C- and A,D-Bridged Calix[6]arene as Stationary Phases in Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 679-682 
    Details
    ISSN: 0935-6304
    Keywords: A,C- and A,D-bridged calix[6]arene ; stationary phase ; capillary gas chromatography ; geometric and positional isomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A,C-Bridged (ACCX) and A,D-bridged isopropyldimethylsilylcalix[6]arene (ADCX) dissolved in OV-1701 were used as stationary phases in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated are well resolved on the two phases. Retention of all the solutes investigated is longer on ACCX than on ADCX. The longer retention on A,C-bridged calix[6]arene is probably due to extra inductive interactions of the solute molecule with the carbonyl moieties in the phase. Separation factors for closely eluting isomer pairs are similar on the two phases. This seems to indicate that the carbonyl moieties do not play an appreciable role in discriminating the isomer molecules on entering the cavity of the calixarene if the solute is retained by the inclusion process.
    Additional Material: 2 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Proton-transfer reactions within ionized methanol clusters: Mass spectrometric and molecular orbital studies (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 969-976 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proton-transfer reactions that proceed within methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. When CH3OH seeded in helium is expanded and ionized by electron impact, the protonated species, (CH3OH)nH+, are the predominant cluster ions in the low-mass region. In CH3OD clusters, both (CH3OD)nH+ and (CH3OD)nD+ ions are observed. The ion abundance ratios, (CH3OD)nH+/(CH3OD)nD+, show a tendency to decrease as the methanol concentration increases, which is apparently related to the cluster structure and reaction energetics. The results suggest that the effective formation of (CH3OD)nH+ ions at low concentration of CH3OD in the expansion is the result of the relatively facile rotation of methanol molecules within the smaller clusters that tend to form at low CH3OD concentration. Ab initio molecular orbital calculations were carried out to investigate the rearrangement and dissociative pathways of ionized methanol dimer. Ion-neutral complexes, [CH3OH2+…O(H)CH2] and [CH3OH2+…OCH3], are found to play an important role in the low-energy pathways for production of CH3OH2+ + CH2OH (and OCH3) from ionized methanol dimer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300706
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  • 3
    Electronic Resource
    Electronic Resource
    Organizational forms of actin in 13762 ascites mammary tumor cell microvilli (1983)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 3 (1983), S. 491-500 
    Details
    ISSN: 0886-1544
    Keywords: actin ; microfilaments ; oligomers ; transmembrane glycoprotein ; microvilli ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The organization of microvillus actin and its associated proteins have been investigated in sublines of mammary ascites tumors (MAT) with mobile (MAT-B1) and immobile (MAT-C1) cell surface receptors. Microvilli isolated from these sublines differ in morphology (branched for MAT-C1 versus unbranched for MAT-B1) and the presence of a 58,000-dalton polypeptide (58K). 58K is found associated with MAT-C1 microvilli, microvillar cytoskeletons obtained by nonionic detergent extractions, and microvillar membranes prepared under conditions which depolymerize actin microfilaments. By extraction with actin-stabilizing buffers (isotonic Triton-Mg-ATP) microvillar actin can be fractionated into four forms. About 40% of the actin is sedimented at low speed (7,500g, 15 min). The pellets contain microfilaments; actin and α-actinin are the predominant proteins. High-speed pellets from these low-speed supernates contain about 10% of the actin as a transmembrane complex with a cell surface glycoprotein (cytoskeleton-associated glycoprotein, [CAG] 75-80,000 daltons) in MAT-B1 cells or with CAG and 58K in MAT-C1 cells. Transmembrane complexes can be purified from MAT-B1 and MAT-C1 microvillar membranes in Triton-containing buffer by gel filtration or sucrose density gradient centrifugation. The presence of only CAG and actin in the MAT-B1 transmembrane complex strongly suggests the direct interaction of actin and a cell surface component. The high-speed supernates contain soluble actin. By gel filtration or rate-zonal sucrose density gradient centrifugation about 30% of the microvillar actin is found as small oligomers and about 10% as G-actin in this extraction buffer. We suggest that the actin-containing transmembrane complexes may serve as membrane-association sites for oligomeric actin segments and microfilaments and as initiation sites for actin polymerization.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970030516
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of different heptakis(6-O-alkyldimethylsilyl-2-3-di-O-ethyl)-β-cyclodextrins as chiral stationary phases in capillary GC (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 437-441 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Enantiomer resolution ; Chiral stationary phase ; Derivated cyclodextrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three new β-cyclodextrin derivatives, heptakis(6-O-isopropyldi-methylsilyl-2,3-di-O-ethyl)-β-cyclodextrin, heptakis(6-O-thexyldi-methylsilyl-2,3-di-O-ethyl)-β-cyclodextrin, and heptakis(6-O-cy-clohexyldimethyl-2,3-di-O-ethyl)-β-cyclodextrin (IPDE-β-CD, TXDE-β-CD, and CHDE-β-CD), were synthesized and the enan-tioselectivities of these three CD derivatives and heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-ethyl)-β-cyclodextrin (TBDE-β-CD) were compared for GC separation of a range of chiral test com-pounds. In particular TXDE-β-CD showed much higher enentio-selectivity than TBDE-β-CD. Enentioselectivities of IPDE-β-CD and CHDE-β-CD are somewhat lower than that of TXDE-β-CD and CHDE-β-Cd are somewhat lower than that of TXDE-β-CD. These observations are indicative of significant effects of subtle changes in the structure of the 6-O-substituent on the enantioselec-tivity of the β-CD derivatives. The difference in enantioselectivities of the 6-O-substituted CD derivatives were explained in terms of relative contributions of the effects of hydrophobicity and steric hindrance of the substituent to the inclusion process. CHDE-β-CD showed the lowest enantioselectivity among the threederivatives. It is likely that the unfavorable steric hindrance of the bulky cyclo-hexyl group plays a greater role than the favorable hydrophobicity effect of the cyclohexyl group in the inclusion process in CHDE-β-CD. IPDE-β-CD showed lower selectivity than TXDE-β-CD and TBDE-β-CD. In the case of these CD derivatives having acyclic substituents the relative hydrophobicity of the substituent seems to be a dominant factor affecting the inclusion process. Isopropyl groups factor affecting the inclusion process. Isopropyl groups are less hydrophobic than thexyl and tert-butyl groups.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240200808
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  • 5
    Electronic Resource
    Electronic Resource
    Intermediates and Side-Reactions in the Synthesis of Molecular Diphenolatonickel Compounds Containing Trimethylphosphane Ligands (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 2027-2032 
    Details
    ISSN: 1434-1948
    Keywords: Nickel(0) ; Oxidation ; Phenols ; Structure ; Ion pairs ; Hydrogen bonds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Admission of molecular oxygen to a solution containing Ni(PMe3)4 and substituted phenols (ArOH) affords bisphenolatonickel compounds trans-Ni(OAr)2(PMe3)2 [ArOH = 2-chlorophenol (1), 2-bromophenol (2), 2,4,6-trichlorophenol (3)]. In the absence of dioxygen the phenols reversibly protonate the nickel complex to form ionic compounds [NiH(PMe3)4]+ Y- containing hydrogen-bonded anions Y = [H2(2-Cl-C6H4O)3] (4), [H(2-OH-C6H4COO)2] (5). As a side-reaction, formal insertion of nickel to give 2-hydroxyphenylnickel compounds Ni(Ar′)X(PMe3)3 [Ar′ = 2-OH-C6H4; × = Br (6), I (7)], trans-Ni(Ar′)Cl(PMe3)2 [Ar′ = 2-OH-3,5-Cl2-C6H2 (8)] and trans-Ni(OAr)Cl(PMe3)2 [Ar = 2,4,6-Cl3-C6H2 (9)] is observed. An X-ray crystal structure determination of 1 shows a trans square planar arrangement of donor atoms, that of 6shows a distorted square pyramid, while 4 contains tetrahedral nickel cations with a delocalized hydrogen atom and triphenolate anions H2(ArO)3-.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Syntheses and Structures of Molecular Diphenolatonickel Compounds Containing Trimethylphosphane Ligands (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 621-627 
    Details
    ISSN: 1434-1948
    Keywords: Nickel ; Oxidation ; Phenols ; Structure ; Dynamic NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of substituted phenols and dioxygen with Ni(PMe3)4 yields the low-spin tetracoordinate diphenolatonickel compounds Ni(OAr)2(PMe3)2 [ArOH = 2-tert-butylphenol (1), 2-tert-butyl-4-methylphenol (2), 2-tert-butyl-6-methylphenol (3), 2,4-di(tert-butyl)phenol (4), 2-tert-butyl-4-methoxophenol (5), 2-chloro-4-tert-butylphenol (6), 2-isopropylphenol (7), 3-tert-butylphenol (8)]. As is revealed by variable temperature 1H- and 13C-NMR spectroscopy the complexes constitute a mixture of two isomers, each of which can be observed separately at lower temperatures when interconversion is slower. An additional 6-carbaldehyde function transforms the phenolate into a chelating ligand, giving rise to a high-spin hexacoordinate compound Ni(OAr)2(PMe3)2 (9). X-ray crystal-structure determinations of 2 and 3 show a trans square-planar structure, and that of 9 shows a trans octahedral arrangement of donor atoms P2O4. Bulky substituents in the 3- or 4-position, or non-demanding substituents in the 2-position, are less effective in stabilizing molecular diphenolatonickel complexes.
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  • 7
    Electronic Resource
    Electronic Resource
    Carbynehydrido- and Vinylidenehydridoosmium Complexes with Os(PCy3)2 as a Molecular Unit (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 951-957 
    Details
    ISSN: 1434-1948
    Keywords: Osmium ; Alkynes ; Carbyne complexes ; Hydrido complexes ; Vinylidene complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of OsCl3·2H2O with PCy3 leads under reducing conditions either to [OsH6(PCy3)2] (1) or [OsH2Cl2(PCy3)2] (2). Treatment of 2 with terminal alkynes HC≡CR (R = Ph, SiMe3) affords the carbynehydrido complexes [OsHCl2(≡CCH2R)(PCy3)2] (4, 5), of which 5 (R = SiMe3) is easily converted with traces of water into [OsHCl2(≡CCH3)(PCy3)2] (6). Compound 4 (R = Ph) reacts with NaOMe to yield the vinylidenehydridoosmium(II) complex [OsHCl(=C=CHPh)(PCy3)2] (7) which upon treatment with HBF4/OEt2 gives the five-coordinate cationic species [OsHCl(≡CCH2Ph)(PCy3)2]-BF4 (8). The reaction of [OsH3Cl(PCy3)2] (9) with HC≡CC(CH3)2Cl affords a mixture of [OsHCl2(≡CCH=CMe2)(PCy3)2] (10) and [OsCl2(H2)(=CHCH=CMe2)(PCy3)2] (11). Compound 11 is quite labile and by elimination of H2 gives 10. The molecular structure of 10 has been determined by X-ray crystallography.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and Diels-Alder Reactions of Some New (Phthalocyanine)nickel Complexes (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 693-703 
    Details
    ISSN: 1434-1948
    Keywords: (Phthalocyanine)nickel complexes ; Unsymmetrical phthalocyanines ; Isobenzofurans ; Diels-Alder reactions ; Ladder-type molecules ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The octasubstituted (phthalocyanine)nickel complexes 4a,b, soluble in common organic solvents, bearing four dienophilic functionalities were synthesized from the corresponding phthalodinitriles 3a,b and nickel(II) acetate. Reaction of 4a with tetracyclone 5 led to the phthalocyanine-tetracyclone adduct 6 which is a precursor for an intermediate phthalocyanine 7 containing four isobenzofuran moieties. The capability of 7 to react as tetrakis(diene) was demonstrated by its reaction with naphthoquinone. Furthermore, the unsymmetrical phthalocyanines 13 and 16a,b,c containing one dienophilic functionality were synthesized using a statistical approach. Their tetracyclone adducts 17, 18a,b,c can be used for the synthesis of ladder-type phthalocyanine dimers. The dimer 22 was synthesized from 18c and p-benzoquinone via the isobenzofuran intermediate 19 and the benzoquinone adduct 21. For dehydration experiments the naphthoquinone monoadduct 23 was synthesized from 18c. Dehydration of 22 and 23 was carried out successfully with p-toluenesulfonic acid. The Diels-Alder reactions are discussed with respect to the occurring exo/endo ratio.
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  • 9
    Electronic Resource
    Electronic Resource
    Resonance Raman studies of compounds I and II of arthromyces ramosus peroxidase: Close similarities in their Raman spectra but distinct oxygen exchangeability of the Fe=O heme (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 2 (1996), S. 317-329 
    Details
    ISSN: 1075-4261
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Simultaneous measurements of resonance Raman and absorption spectra were performed for intermediates generated upon addition of hydrogen peroxide to ferric Arthromyces ramosus peroxidase (ARP) using the microcirculating system constructed in this laboratory, which enables generation of desirable intermediates under steady-state conditions. Compound I of ARP generated at neutral pH was stable over tens of minutes in the absence of laser illumination with this circulation system, but was gradually degraded under laser illumination, giving rise to a new irreversible species with an iron-oxo heme. Such photosensitivity was not observed for compound II in the steady state at alkaline pH. Surprisingly, the Raman spectrum of compound I of ARP in the high-frequency region, where characteristic frequency shifts are expected upon oxidation of the macrocycle, was quite close to that of compound II, despite the fact that the reduced Soret absorption indicated the formation of a π-cation radical. The Fe=O stretching (νFe=O) frequency of compound I was observed at 781 cm-1 for the 16O derivative but appeared as a doublet at 744 and 731 cm-1 for the 18O derivative. The isotope sensitivity of the νFe=O mode of compound I was seen upon H216O/H218O solvent substitution but not upon H216O2/H218O2 peroxide substitution in H216O at neutral pH. This directly indicates the occurrence of an oxygen atom exchange between the oxo-heme and bulk water, providing the first example of such exchange in compound I of peroxidases. The oxygen exchange was abolished for compound II at alkaline pH, for which the νFe=o mode was seen at 787/749 cm-1 only upon H216O2/H218O2 peroxide substitution. The oxygen exchangeability seems to depend on protonation of a nearby residue with pKα ∼ 9 and to correlate with stability of compound I. © 1996 John Wiley & Sons, Inc.
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of an Oligo(phenylenevinylene)-Bridged Phthalocyanine Dimer (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1687-1691 
    Details
    ISSN: 1434-193X
    Keywords: Nickel phthalocyanines ; Phthalocyanines ; Diels-Alder reactions ; Polymers ; Wittig reactions ; Cycloadditions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nickel phthalocyanine 4, which is soluble in common organic solvents, has been synthesized from the corresponding tetracyclone monoadduct 1 and acrolein (3). Reaction of 4 with p-toluenesulfonic acid leads to the modified phthalocyanine monoaldehyde 5. The capability of 5 to undergo a Wittig reaction has been demonstrated with benzyltriphenylphosphonium bromide (6). Furthermore, a dimer 9 has been synthesized by treating 5 with 0.5 equiv. of xylylenebis(triphenylphosphonium bromide) (8). Dimer 9 constitutes a model compound for corresponding PPV polymers containing phthalocyanine subunits.
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