Persistence of activity in noisy motor-filament assemblies

TL;DR

This study investigates how active molecular motors influence the mechanical response of elastic filaments in noisy environments, revealing a persistence length scale governed by the balance of passive elasticity and active shear resistance.

Contribution

It extends the understanding of persistence length in active filament systems by analyzing the effects of strong noise and motor-filament coupling through numerical simulations.

Findings

Persistence length depends on the ratio of passive elasticity to active shear resistance.

Active noise causes deviations from mean field predictions but retains qualitative features.

The work generalizes passive persistence concepts to active, noisy systems.

Abstract

Long, elastic filaments cross-linked and deformed by active molecular motors occur in various natural settings. The overall macroscopic mechanical response of such a composite network depends on the coupling between the active and the passive properties of the underlying constituents and nonlocal interactions between different parts of the composite. In a simple one dimensional system, using a mean field model, it has been shown that the combination of motor activity and finite filament extensibility yields a persistence length scale over which strain decays. Here we study a similar system, in the complementary limit of strong noise and moderate extensibility, using Brownian multi-particle collision dynamics-based numerical simulations that includes the coupling between motor kinetics and local filament extensibility. While the numerical model shows deviations from the mean field predictions due to the presence of strong active noise caused by the variations in individual motor activity, several qualitative features are still retained. Specifically, for fixed motor attachment and detachment rates, the decay is length is set by the ratio of the passive elasticity to the active shear resistance generated by attached motors. Our study generalizes the notion of persistence in passive thermal systems to actively driven systems with testable predictions.