Non-equilibrium fluctuations of a semi-flexible filament driven by active cross-linkers

TL;DR

This paper models the non-equilibrium fluctuations of semi-flexible cytoskeletal filaments influenced by active cross-linkers, revealing a characteristic bending spectrum and deviations caused by localized forces and non-thermal dynamics.

Contribution

It introduces a coupled model of filament deformation and stochastic cross-linker dynamics, providing insights into non-thermal fluctuation spectra in active biological networks.

Findings

Bending spectrum exhibits a q^{-2} dependence under certain conditions.

Localized forcing and non-thermal effects cause deviations from thermal-like spectra.

The model captures biologically relevant fluctuation behaviors of cytoskeletal filaments.

Abstract

The cytoskeleton is an inhomogeneous network of semi-flexible filaments, which are involved in a wide variety of active biological processes. Although the cytoskeletal filaments can be very stiff and embedded in a dense and cross-linked network, it has been shown that, in cells, they typically exhibit significant bending on all length scales. In this work we propose a model of a semi-flexible filament deformed by different types of cross-linkers for which one can compute and investigate the bending spectrum. Our model allows to couple the evolution of the deformation of the semi-flexible polymer with the stochastic dynamics of linkers which exert transversal forces onto the filament. We observe a $q^{-2}$ dependence of the bending spectrum for some biologically relevant parameters and in a certain range of wavenumbers $q$. However, generically, the spatially localized forcing and the non-thermal dynamics both introduce deviations from the thermal-like $q^{-2}$ spectrum.