Tensile elasticity of semiflexible polymers with hinge defects

TL;DR

This paper analytically investigates how hinge defects affect the tensile elasticity of semiflexible polymers, revealing increased compliance and entropic elasticity, with implications for biopolymers like DNA and cytoskeletal filaments.

Contribution

It introduces an analytical model for wormlike chains with hinge defects, extending understanding of their force-extension behavior under tension.

Findings

Hinge defects increase differential tensile compliance.

Hinge defects significantly enhance entropic elasticity at low forces.

Model applies to various semiflexible segments, including biopolymers and cytoskeletal filaments.

Abstract

It has become clear in recent years that the simple uniform wormlike chain model needs to be modified in order to account for more complex behavior which has been observed experimentally in some important biopolymers. For example, the large flexibility of short ds-DNA has been attributed to kink or hinge defects. In this paper, we calculate analytically, within the weak bending approximation, the force-extension relation of a wormlike chain with a permanent hinge defect along its contour. The defect is characterized by its bending energy (which can be zero, in the completely flexible case) and its position along the polymer contour. Besides the bending rigidity of the chain, these are the only parameters which describe our model. We show that a hinge defect causes a significant increase in the differential tensile compliance of a pre-stressed chain. In the small force limit, a hinge defect significantly increases the entropic elasticity. Our results apply to any pair of semiflexible segments connected by a hinge. As such, they may also be relevant to cytoskeletal filaments (F-actin, microtubules), where one may treat the cross-link connecting two filaments as a hinge defect.