Tension-induced binding of semiflexible biopolymers

TL;DR

This paper models how tension influences reversible cross-linking in biopolymers, revealing a tension-induced transition that enhances force-stiffening beyond single-chain elasticity.

Contribution

It introduces a theoretical framework linking tension to cross-link binding behavior and force-stiffening in semiflexible biopolymers, highlighting a tension-driven transition mechanism.

Findings

Tension causes a sudden increase in bound cross-links.

A free-energy barrier governs reversible binding/unbinding.

Transition relates to localization crossover in directed polymers.

Abstract

We investigate theoretically the effect of polymer tension on the collective behavior of reversibly binding cross-links. For this purpose, we employ a model of two weakly bending wormlike chains aligned in parallel by a tensile force, with a sequence of inter-chain binding sites regularly spaced along the contours. Reversible cross-links attach and detach at the sites with an affinity controlled by a chemical potential. In a mean-field approach, we calculate the free energy of the system and find the emergence of a free-energy barrier which controls the reversible (un)binding. The tension affects the conformational entropy of the chains which competes with the binding energy of the cross-links. This competition gives rise to a sudden increase in the fraction of bound sites as the tension increases. We show that this transition is related to the cross-over between weak and strong localization of a directed polymer in a pinning potential. The cross-over to the strongly bound state can be interpreted as a mechanism for force-stiffening of cross-linked polymers -- beyond the elasticity of a single wormlike chain.