Intramolecular conformational transitions "random coil-helix-folded structure" in polypeptides.

Abstract

AbstractA general theory has been developed for conformational intramolecular transitions in a single macromolecule with a high degree of polymerization (an infinite length model) capable of forming two types of ordered structures: the α‐helix and the folded β‐structure, as well as acquiring the random coil conformation. The phase diagram analysis of this system has shown that the regular β‐structure state is separated from all other states of the chain by the phase boundary line. Any intersection of the phase boundary is a phase transition which can be either of the first order or second order, depending on values of the energy parameters of the system. Mechanisms of intramolecular rearrangements: β‐structure–random coil and α‐helix–β‐structure have been discussed. It has been shown that there exist two different mechanisms for each of these rearrangements, and the regions of parameter variation corresponding to each mechanism have been specified.