Conformational transitions of heteropolymers in dilute solutions

TL;DR

This paper extends a Gaussian self-consistent method to analyze the equilibrium and kinetic conformational transitions of heteropolymers with arbitrary sequences, revealing complex phase diagrams and multistep folding kinetics.

Contribution

It introduces a new approach to study heteropolymer conformations and kinetics, including stability analysis and phase diagram construction for various sequences.

Findings

Identified multiple conformational phases including coil, globule, and frustrated states.

Discovered that certain sequences suppress frustrated phases.

Revealed multistep, glassy-like folding kinetics.

Abstract

In this paper we extend the Gaussian self-consistent method to permit study of the equilibrium and kinetics of conformational transitions for heteropolymers with any given primary sequence. The kinetic equations earlier derived by us are transformed to a form containing only the mean squared distances between pairs of monomers. These equations are further expressed in terms of instantaneous gradients of the variational free energy. The method allowed us to study exhaustively the stability and conformational structure of some periodic and random aperiodic sequences. A typical phase diagram of a fairly long amphiphilic heteropolymer chain is found to contain phases of the extended coil, the homogeneous globule, the micro-phase separated globule, and a large number of frustrated states, which result in conformational phases of the random coil and the frozen globule. We have also found that for a certain class of sequences the frustrated phases are suppressed. The kinetics of folding from the extended coil to the globule proceeds through non-equilibrium states possessing locally compacted, but partially misfolded and frustrated, structure. This results in a rather complicated multistep kinetic process typical of glassy systems.