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  • Polymer and Materials Science  (9)
  • Biochemistry and Biotechnology  (2)
  • Wiley-Blackwell  (11)
  • Wiley
  • 1985-1989  (11)
  • 1
    Electronic Resource
    Electronic Resource
    The hydrogen bonding of cytosine with guanine: Calorimetric and 1H-NMR analysis of the molecular interactions of nucleic acid bases (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 591-603 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enthalpy of hydrogen-bond formation between guanine (G) and cytosine (C) in o-dichlorobenzene and in chloroform at 25°C has been determined by direct calorimetric measurement. We derivatized 2′-deoxyguanosine and 2′-deoxycytidine at the 5′- and 3′-hydroxyls with triisopropylsilyl groups; these groups increase the solubility of the nucleic acid bases in nonaqueous solvents. Such derivatization also prevents the ribose hydroxyls from forming hydrogen bonds. Consequently, hydrogen-bond formation in our system is primarily between the bases, and to a lesser extent, between base and solvent, and can be measured directly with calorimetry. To obtain the data on base-pair formation, we first took into account the contributions from self-association of each base, and where possible, have determined the ΔH of self-association. From isoperibolic titration calorimetry, our measured ΔH of C2 formation in chloroform is -1.7 kcal/mol of C. Our measured ΔH of C:G base-pair formation in o-dichlorobenzene is -6.65 ± 0.32 kcal/mol. Since o-dichlorobenzene does not form hydrogen bonds, the ΔH of C:G base-pair formation in this solvent represents the ΔH of the hydrogen-bonding interaction of C with G in a nonassociating solvent. In contrast, our measured ΔH of C:G base-pair formation in chloroform is -5.77 ± 0.20 kcal/mol; thus, the absolute value of the enthalpy of hydrogen bonding in the C:G base pair is greater in o-dichlorobenzene than in chloroform. Since chloroform is a solvent known to form hydrogen bonds, the decrease in enthalpic contribution to C:G base pairing in chloroform is due to the formation of hydrogen bonds between the bases and the solvent. The ΔH of hydrogen bonding of G with C reported here differs from previous indirect estimates: Our measurements indicate the ΔH is 50% less in magnitude than the ΔH based on spectroscopic measurements of the extent of interaction. We have also observed that the enthalpy of hydrogen bonding of C with G in chloroform is greater when G is in excess than when C is in excess. This increased heat is due to the formation of C:Gn 〉 1 complexes that we have observed using 1H-nmr. Although C:G2 structures have previously been observed in triple-stranded polymeric nucleic acids, higher order structures have not been observed between C and G monomers in nonaqueous solvents until now. By using monomers as a model system to investigate hydrogen-bonding interactions in DNA and RNA, we have obtained the following results: A direct measurement of the ΔH of hydrogen bonding in the C:G complex in two nonaqueous solvents, and the first observation of C:Gn 〉 1 complexes between monomers. These results reinforce the importance of hydrogen bonding in the stabilization of various nucleic acid secondary and tertiary structures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260411
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  • 2
    Electronic Resource
    Electronic Resource
    Purification of thermotropic liquid-crystalline siloxane oligomer with supercritical carbon dioxide (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1407-1412 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of the purification of thermotropic liquid-crystalline siloxane oligomer with supercritical carbon dioxide were investigated. It was found that low-molar-mass contaminants, presumably the two alkene precursors, can be effectively removed at 80°C and carbon dioxide pressures up to 31,0 MPa. In support of this observation is the fact that glass transition temperature goes up as a result of purification. In addition, the selective reflection wavelength was found to increase at increasing purity level, as achieved by extraction at increasing carbon dioxide pressure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900620
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  • 3
    Electronic Resource
    Electronic Resource
    An infrared spectroscopic investigation of the phase behavior of a polydiacetylene. The case of polydiacetylene with side groups containing a urethane function (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 2557-2567 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The infrared spectrum of polydiacetylene with side chains containing urethane functions (1) was analyzed. Based on the polarization data and the changes observed as a function of temperature, the multiple bands in the Amide I region observed for the film sample were attributed to the transition dipole coupling mechanism. The consequences of this new assignment illustrate the difficulty in using vibrational spectroscopy as a definitive tool to characterize the relationship between structural reorganization of the side chain and the chromic transition at high temperature.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021861217
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic characterization of the chromic transition observed for polydiacetylenes (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2311-2316 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The chromic transition observed for polydiacetylene CHCl3/CCl4 solutions was found to be concentration dependent suggesting a need to reconsider the hypothesis that this transition is a single chain phenomenon. We also found that for some polydiacetylene solutions this chromic transition exhibits a significant amount of hysteresis for the cooling and heating cycles.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021881007
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  • 5
    Electronic Resource
    Electronic Resource
    Spectroscopic characterization of chromic transition in polydiacetylenes, 3Part 2: cf. ref.8, part 1: cf. ref.11. (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2679-2686 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: From optical absorption and infrared data, we have been able to establish the existence of a direct relationship between the weakening of the hydrogen-bonding properties of the side-chain and the chromic transition of the main chain for poly{1,2-bis{4-[N-(butoxycarbonylmethyl)-carbamoyloxy]butyl}-1-buten-3-ynediyl} (poly4BCMU), a family of soluble polydiacetylenes disubstituted with 4-[N-(butoxycarbonylmethyl)carbamoyloxy]butyl side chains. This observation is in contrast to the lack of correlation found for polydiacetylene film. Our data also show that this chromic transition is unaffected by the gelation process found for this family of polydiacetylenes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021881118
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of the thermal degradation of alkyl isocyanate polymers by direct pyrolysis mass spectrometry (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 3211-3225 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal degradation mechanisms of alkyl isocyanate homo- and copolymers were studied using TGA and DP-MS. Both analyses showed that these polymers begin decomposing at around 190°C under inert or vacuum conditions. DP-MS analysis showed the formation of trace quantities of monomer from poly(butyl isocyanate) only and none from higher homologs. All polymers studied produced trimers as their principal decomposition product, implying that intramolecular cyclization is the dominant mechanism of decomposition.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1989.080271003
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation of various glucose esters via lipase-catalyzed hydrolysis of glucose pentaacetate (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 648-651 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: β-D(+)-Glucose pentaacetate was hydrolyzed both chemically and enzymatically. In contrast to the alkaline hydrolysis, esterase-catalyzed deacetylations afforded significant accumulation of intermediate glucose esters at different degrees of substrate conversion. Aspergillus niger lipase, the most suitable of the four enzymes tested, was used for preparative hydrolysis of glucose pentaacetate. As a result, gram quantities of pure glucose-2,3,4,6-tetraacetate, glucose triacetate (a mixture of two positional isomers, 2,4,6- and 3,4,6-), and glucose-4,6-diacetate were prepared.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290515
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  • 8
    Electronic Resource
    Electronic Resource
    Lipase-catalyzed oil hydrolysis in the absence of added emulsifier (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 628-633 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260310618
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of fiber orientation on the stress distribution in model composites (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 2605-2619 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A Raman-mechanical technique was used to study the relationship between stress distribution and fiber orientation in model composites. Our experimental data generally were consistent with most simplistic mechanical models. A more complete analysis, using the Eshelby equivalent inclusion method, fitted our experimental data exceptionally well. For large applied strains, compressive failure occurred for fibers which were oriented at high angles relative to the draw direction. This occurred because of the lateral shrinkage associated with the matrix when the sample was stretched. The effect of fiber end geometry on the stress distribution for these misaligned fibers was the same as observed earlier. Tapered-end fibers generally carried loads more efficiently in composites than blunt-end fibers.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090271304
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanical behavior of polyblended polystyrene and ethylene-propylene-diene rubber by cationic reactions in the melt (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1677-1683 
    Details
    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: Attempts have been made to obtain high impact polystyrene by Lewis-acid-initiated degradation process in the melt reactions of PS and EPDM. It is found that impact strength improves whereas tensile strength decreases. This can be interpreted by the increased solubility of the coupled rubber molecules in the continuous phase.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380908
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