Semiflexible polymer in a gliding assay: reentrant transition, role of turnover and activity

TL;DR

This study models a semiflexible filament in a motility assay, revealing a first-order phase transition to spiral conformations with reentrant behavior influenced by activity and turnover, affecting polymer shape and dynamics.

Contribution

It introduces a detailed model of active semiflexible filaments with load-dependent motor interactions, uncovering a reentrant transition and complex dynamical behaviors not previously characterized.

Findings

Filament undergoes a first-order transition from open to spiral conformations.

Reentrant behavior observed in active extension and turnover rates.

Correlation functions exhibit double-exponential decay with a maximum correlation time.

Abstract

We consider a model of an extensible semiflexible filament moving in two dimensions on a motility assay of motor proteins represented explicitly as active harmonic linkers. Their heads bind stochastically to polymer segments within a capture radius, and extend along the filament in a directed fashion before detaching. Both the extension and detachment rates are load-dependent and generate an active drive on the filament. The filament undergoes a first order phase transition from open chain to spiral conformations and shows a reentrant behavior in both the active extension and the turnover, defined as the ratio of attachment-detachment rates. Associated with the phase transition, the size and shape of the polymer changes non-monotonically, and the relevant autocorrelation functions display double-exponential decay. The corresponding correlation times show a maximum signifying the dominance of spirals. The orientational dynamics captures the rotation of spirals, and its correlation time decays with activity as a power law.