Theory of single-molecule experiments in the overstretching force regime

TL;DR

This paper develops a statistical mechanics framework for understanding the elasticity of biopolymers under high force, unifying different experimental setups and demonstrating a universal model for force-extension behavior across polymer lengths.

Contribution

It introduces a comprehensive theoretical approach to single-molecule stretching, connecting constant-force and constant-displacement experiments, and shows universality in force-extension curves.

Findings

Force-extension curves are universal across different polymers.

Constant-force and constant-displacement formulations converge in the thermodynamic limit.

Monte Carlo simulations support the theoretical model.

Abstract

We present a statistical mechanics analysis of the finite-size elasticity of biopolymers, consisting of domains which can exhibit transitions between more than one stable state at large applied force. The constant-force (Gibbs) and constant-displacement (Helmholtz) formulations of single molecule stretching experiments are shown to converge in the thermodynamic limit. Monte Carlo simulations of continuous three dimensional polymers of variable length are carried out, based on this formulation. We demonstrate that the experimental force-extension curves for short and long chain polymers are described by a unique universal model, despite the differences in chemistry and rate-dependence of transition forces.