Forced desorption of semiflexible polymers, adsorbed and driven by molecular motors

TL;DR

This study models the behavior of semiflexible polymers with motor proteins under force, revealing how active forces induce desorption and characterizing the phase transition through simulations and theoretical analysis.

Contribution

It introduces a combined simulation and theoretical framework to analyze motor-driven polymer desorption, highlighting the effects of activity, rigidity, and motor processivity.

Findings

Desorption occurs at a threshold force dependent on polymer rigidity.

Correlation time diverges near complete desorption, following a power law.

Desorption force increases with motor activity and polymer stiffness.

Abstract

We formulate and characterize a model to describe the dynamics of semiflexible polymers in the presence of activity due to motor proteins attached irreversibly to a substrate, and a transverse pulling force acting on one end of the filament. The stochastic binding-unbinding of the motor proteins and their ability to move along the polymer, generates active forces. As the pulling force reaches a threshold value, the polymer eventually desorbs from the substrate. Performing molecular dynamics simulations of the polymer in presence of a Langevin heat bath, and stochastic motor activity, we obtain desorption phase diagrams. The correlation time for fluctuations in desorbed fraction increases as one approaches complete desorption, captured quantitatively by a power law spectral density. We present theoretical analysis of the phase diagram using mean field approximations in the weakly bending limit of the polymer and performing linear stability analysis. This predicts increase in the desorption force with the polymer bending rigidity, active velocity and processivity of the motor proteins to capture the main features of the simulation results.