Kinetics of the helix-coil transition

TL;DR

This paper investigates the kinetics of helix-coil transitions in biopolymers using the Zimm-Bragg model, revealing hysteresis, non-equilibrium phases, and anomalous responses during finite-speed temperature changes.

Contribution

It introduces a detailed analysis of non-equilibrium effects and hysteresis in helix-coil transitions driven by finite-speed temperature variations.

Findings

Helix-to-coil transition occurs faster and is observable at finite speeds.

Hysteresis effect explains experimental observations.

Non-equilibrium phases exhibit larger correlation lengths and anomalous thermal responses.

Abstract

Based on the Zimm-Bragg model we study cooperative helix-coil transition driven by a finite-speed change of temperature. There is an asymmetry between the coil-to-helix and helix-to-coil transition: the latter is displayed already for finite speeds, and takes shorter time than the former. This hysteresis effect has been observed experimentally, and it is explained here via quantifying system's stability in the vicinity of the critical temperature. A finite-speed cooling induces a non-equilibrium helical phase with the correlation length larger than in equilibrium. In this phase the characteristic length of the coiled domain and the non-equilibrium specific heat can display an anomalous response to temperature changes. Several pertinent experimental results on the kinetics helical biopolymers are discussed in detail.