Strain Stiffening Induced by Molecular Motors in Active Crosslinked Biopolymer Networks

TL;DR

This study models molecular motors in biopolymer networks to understand how they induce strain stiffening, revealing that compliant crosslinks lead to significantly greater stiffening than rigid ones, aligning with experimental data.

Contribution

It introduces a finite element model of molecular motors as force dipoles to explain strain stiffening differences based on crosslink compliance.

Findings

Compliant crosslinks cause up to 100-fold stiffening.

Rigid crosslinks result in only about twofold stiffening.

Motor-induced deformation primarily affects compliant crosslinked networks.

Abstract

We have studied the elastic response of actin networks with both compliant and rigid crosslinks by modeling molecular motors as force dipoles. Our finite element simulations show that for compliant crosslinkers such as filamin A, the network can be stiffened by two orders of magnitude while stiffening achieved with incompliant linkers such as scruin is significantly smaller, typically a factor of two, in excellent agreement with recent experiments. We show that the differences arise from the fact that the motors are able to stretch the compliant crosslinks to the fullest possible extent, which in turn causes to the deformation of the filaments. With increasing applied strain, the filaments further deform leading to a stiffened elastic response. When the crosslinks are incompliant, the contractile forces due to motors do not alter the network morphology in a significant manner and hence only small stiffening is observed.