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  • Chemistry  (101)
  • Polymer and Materials Science  (45)
  • LUNAR AND PLANETARY EXPLORATION
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 332-338 
    ISSN: 0006-3592
    Keywords: α-hydroxynitrile lyase ; cassava ; cyanogenesis ; cyanohydrin ; Escherichia coli expression vector ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The coding sequence of the cyanogenic α-hydroxynitrile lyase gene of Manihot esculenta Crantz (cassava) was cloned in the plasmid vector pMal-c2 and expressed in Escherichia coli strain JM105. DNA sequencing showed that the recombinant plasmid contained the same sequence as the cDNA clone pHNL10. Peptide sequencing of the recombinant protein showed that the N-terminus was heterogeneous, with either four or six additional amino acid residues compared with the native protein. Circular dichroism spectra indicated similar secondary structure contents for both proteins. Enzyme assays showed that specific activity of native and recombinant proteins were 0.24 and 0.26 mmol CN-/mg/min, respectively; that both proteins had optimal activity at 40°C and pH 5.5; and that both proteins were inhibited by the serine protease inhibitor phenyl-methane sulfonyl flouride (PMSF). Isoelectric focusing of native and recombinant protein revealed multiple isoforms for both proteins; the recombinant protein had a more basic mean isoelectric point (pl) (5.1) than the native protein (4.5). © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 332-338, 1997.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 4 (1966), S. 1081-1090 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies were made of the influence of hydrostatic pressure on the helix-coil transitions of poly (A + U) and poly (A + 2U). The results were analyzed by a thermodynamic treatment which emphasized the cooperative aspect of the transitions. The helix-to-coil volume changes were found to be small and negative indicating pressure stabilization of the coil form. The significance of the results with respect to other denaturation measurements was discussed.
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  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variable-temperature proton nmr spectra of the oligoribonucleotides in the series CpApX and the series ApGpX, X = A, G, C, U, together with the parent dimers CpA and ApG have been measured. A complete analysis of all the nonexchangeable base proton resonances and ribose H-1′ proton resonances was made. The presence of trends in the shielding abilities of the various bases at both the nearest-neighbor and next-nearest-neighbor positions were identified. The observed shieldings could be used to predict the chemical shifts of protons in related systems. Based on the empirical results from ribodinucleoside monophosphates, the temperature-dependent behavior of the J1′2′ coupling constants of the triribonucleotides suggested that the compounds in the CpApX series stacked from the 5′-end to the 3′-end, while those in the ApGpX series stacked from the 3′-end to the 5′-end.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions of calf thymus DNA have been degraded in the presence of vibrating air bubbles in ultrasonic fields of low power which would not normally induce ultrasonic cavitation. The DNA was degraded to a limiting intrinsic viscosity, after which further irradiation by ultrasound had little or no effect. This limiting intrinsic viscosity decreased with increase in the ultrasonic intensity. Previously developed theories have-been adapted to calculate the maximum velocity gradient associated with the streaming of the solution around such vibrating air bubbles. The tensile force which is induced and which acts on the DNA has been calculated on the basis of current theories of degradation by hydrodynamic shear. These calculations indicate that the degradation of the DNA by ultrasound under conditions of “stable cavitation” is mainly the result of the shearing forces engendered in the solution around the oscillating bubbles.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 169-179 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic cyclic octapeptides of general structure cyclo[Glu(γOBzl)-Sar-Gly-(N-R)Gly]2 (R = n-hexyl and cyclohexyl) transport calcium ions selectively across organic phases and phospholipid membranes. We have now used proton nmr spectroscopy (360 MHz) to study the solution conformation(s) of their calcium complexes. When Ca(ClO4)2 was added to solutions of these peptides in CDCl3, nmr spectra of the resulting calcium complexes were characteristic of a single C2-symmetric conformer. From a Karplus-Bystrov analysis of vicinal coupling constants in both the peptide backbone and Glu side chain (treated as an ABCC′MX spin system), in conjuction with model-building studies, a structure was proposed in which the calcium ion is bound in an octahedral-type complex by the four (coplanar) carbonyl groups of the (all-trans) Glu-Sar and Gly-(N-R)Gly peptide bonds. Occurrence of preferred rotamers about Glu side chain Cα-Cβ bonds indicated that restricted rotation in peptide side chains arises upon calcium binding.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Separate neutral aqueous solutions of either (a) methylcob(III)alamin (2) and (heptamethyl cob(II)yrinate) perchlorate (3) or of b) cob(II)alamin ( = vitamin B12r; (4) and [Coβ-methyl(heptamethyl cob(III)yrinate)] perchlorate (5) equilibrated thermally at r.t. according to 2 + 3 ⇄ 4 + 5. The corresponding equilibrium constant Ke was determined (Ke = 0.63 ± 0.15). This equilibration experiment indicates that the coordination of the nucleotide function in methylcob(II)alamin (2) hardly affects the thermodynamics of the Co—C bond homolysis in aqeous solution when compared to nucleotide-free methylcorrinoids such as 5.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 1724-1725 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [2 + 2]-Cycloaddition of an Iminoborane to a Methylene-Titanium Coordination CompoundThe iminoborane tBuB ≡ NtBu (1c) reacts with the short-lived titanaethene H2C = TiCp2 (3) to give the 1-aza-2-bora-4-titanacyclobutane 4c by [2 + 2]-cycloaddition. A corresponding reaction with the more reactive iminoboranes 1a, b, d is indicated by NMR data.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 465-474 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A systematic study of the effect of potassium hydroxide on the autoxidation of poly(propylene oxide)s with number average molecular weights, M̄n, in the range 400-3000 has been made in the range of temperature 110-140°C. For all the polymers a considerable increase in the induction time was produced by KOH in solution in the polymer, the increase being most marked for the polymer of lowest molecular weight. For the polymers of molecular weight 1000 and lower, the rate of the subsequent autoxidation was considerably reduced by the KOH, the effect being greatest for the polymer of molecular weight 400. For polymers of molecular weight 2000 and above no change in rate was observed. The effectiveness of KOH as an antioxidant is shown to depend on the concentration of terminal hydroxyl groups and is explained by the non-radical decomposition of RO-2 ions.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 781-788 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerization of acrylamide with allyl glycidyl ether yielded water soluble polymers containing an epoxy group; addition of a crosslinking agent, N,N′-methylenebis(acrylamide), to the copolymerization mixtures resulted in the formation of similar though water insoluble polymers. Condensation of a potent beta-adrenergic antagonist Alm—H, which contains a reactive amino group, with a polymer containing an epoxy group yeilded a pharmacologically active polymer. The polymer containing the epoxy group was also converted, by reaction with sodium thiosulfate and subsequent reduction, into a mecapto groups containing polymer which was also water soluble. The latter polymer was converted by condensation with a beta-adrenergic antagonist Alm—COCH2Br, which contains a reactive bromoacetamido group, into a pharmacologically active polymer.
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  • 10
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An infrared method has been developed for the determination of the isotacticity of polypropylene in the 90-100% range. The method requires the annealing of thin films at 165-167°C. for 3 hr. in an inert atmosphere, followed by slow cooling to room temperature. For approximate answers the ratio of the intensity of the 10.00 μ band to that of the 10.27 μ band can be reported as the fraction of isotactic material. Better results are obtained, however, by using Figure 2 as a calibration curve and reading the values from it.
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