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
Permalink
