Premium
Enthalpies of helix–coil transitions in polypeptides
Author(s) -
Karasz F. E.,
Gajnos G. E.
Publication year - 1974
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1974.360130407
Subject(s) - chemistry , dichloroacetic acid , random coil , enthalpy , solvent , electromagnetic coil , helix (gastropod) , thermodynamics , isothermal process , crystallography , organic chemistry , circular dichroism , physics , ecology , quantum mechanics , biology , snail
Certain discrepancies in measured heats of helix–coil transitions in polypeptides are examined in terms of the theory of the effect of solvent composition on transition temperatures and heats in such systems. It is found, generally, that disagreement between enthalpy measurements conducted at fixed solvent compositions and isothermally may be expected because of the possibility of incomplete conversion of the polypeptide from the random‐coil to the helical conformations, or vice versa in one, or both, of these regimes in the course of the transition. The magnitude of the disagreement, if any, can depend quite critically on the particular region in the transition temperature–solvent composition plane in which measurements are undertaken. Application of these results to the system, poly‐γ‐benzyl‐ L ‐glutamate–dichloroacetic acid‐1,2‐dichloroethane, however, suggests that previously observed discrepancies in enthalpies here cannot be attributed to this phenomenon.