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  • Wiley-Blackwell  (3)
  • 1970-1974  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Solution properties of synthetic polypeptides. XVI. Hydrogen bonding in helix-coil transitions of poly(β-benzyl L-aspartate) (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1533-1541 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Helix-coil transition of polypeptides in solution involves two elementary processes: unfolding of an α-helical polypeptide chain and interaction of the unfolded chain with solvent molecules which are capable of forming hydrogen bonds. Optical rotation data for poly(β-benzyl L-aspartate) in mixtures of dichloroacetic acid and carbon tetrachloride are analyzed according to the procedure developed by Sayama et al., who explicitly took these processes into theoretical account; and the enthalpy changes, ΔH0 = -650 ± 200 cal/mole and ΔHa = -5.2 ± 1.6 kcal/mole. The latter value is favorably compared with heats of association (per hydrogen bond) of various amides and lactams in CCl4. There is excellent agreement with -5.15 kcal/mole for δ-valerolactam in CCl4. In analogy with amides in non-polar solvents, the difference between ΔH0 and ΔHa may be attributed to the fact that the former is associated with intramolecular hydrogen bonding, whereas the latter is associated with intermolecular hydrogen bonding.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120708
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  • 2
    Electronic Resource
    Electronic Resource
    Solution properties of synthetic polypeptides. XV. Helix-coil transition in poly (ε-carbobenzyloxy L-lysine) (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1515-1532 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Helix-coil transitions of poly(ε-carbobenzyloxy L-lysine) (PCBL) in m-cresol and in mixtures of dichloroacetic acid (DCA) and ethylene dichloride (EDC) were investigated by optical rotation measurements, with special interest in the molecular-weight dependence of helical content. The data obtained were analyzed according to an approximate expression for the helical content of Okita et al. The values obtained for the cooperativity parameter σ and transition enthalpy ΔHε (at the transition temperature) were: √σ = (0.25 ± 0.06) × 10-2 and ΔHc = 930 ± 130 cal/mole in m-cresol, and √σ = (0.49 ± 0.10) × 10-2, and ΔHc = 350 ± 150 kcal/mole in a DCA-EDC mixture (33 vol % DCA). The ΔHc value in the DCA-EDC mixture is much smaller than that derived by Giacometti et al. from heat of solution measurements. The transition in m-cresol was extremely sharp. This was attributed to the unusually small value of √σ and the moderately large value of ΔHc obtained.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120707
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  • 3
    Electronic Resource
    Electronic Resource
    Notes on polymer hydrodynamics (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 899-907 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sedimentation of an unperturbed polymer chain in dilute solution is reformulated by using Burgers' method, in which the no-slip boundary condition on the surface of each chain element is taken into account approximately. It is shown that the forcevelocity proportionality relation employed so far as the basis of theoretical developments in polymer hydrodynamics can be justified as a first approximation to the no-slip condition. The derived expression for the translational friction coefficient ft is a complex function of n and a/b, where n is the number of chain elements in a single molecule and a/b is the ratio of the Stokes radius of a chain element to the effective bond length. Three special cases corresponding mathematically to b = ∞ (no hydrodynamic interaction), a ≪ b (Kirkwood-Riseman theory), and b = 2a (touching-sphere model) are examined in detail. Finally, it is shown that when a/b = 0.2360, our ft varies linearly with n1/2 over the entire range of n.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180110507
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