Transition between globule and stretch states of a self-attracting chain in the repulsive active particle bath

TL;DR

This study uses Brownian dynamics simulations to investigate how self-propelling particles influence the folding and unfolding transitions of a self-attracting chain, revealing distinct mechanisms and hysteresis effects.

Contribution

It uncovers two different transition mechanisms depending on the rotational diffusion rate of active particles and demonstrates how active agents can control polymer conformations.

Findings

Globule-stretch transition is driven by shear at low SPP rotational diffusion.

Collision-induced melting causes transition at high SPP rotational diffusion.

Hysteresis in transition curves appears at low SPP rotational diffusion.

Abstract

Folding and unfolding of biopolymers are often manipulated in experiment by tuning pH, temperature, single-molecule force or shear field. Here we carry out Brownian dynamics simulations to explore the behavior of a single self-attracting chain in the suspension of self-propelling particles (SPPs). As the propelling force increases, globule-stretch (G-S) transition of the chain happens due to the enhanced disturbance from SPPs. Two distinct mechanisms of the transition in the limits of low and high rotational diffusion rates of SPPs have been observed: shear effect at low rate and collision-induced melting at high rate. The G-S and S-G (stretch-globule) curves form hysteresis loop at low rate, while they merge at high rate. Besides, we find two competing effects result in the non-monotonic dependence of the G-S transition on the SPP density at low rate. Our results suggest an alternative approach to manipulating the folding and unfolding of (bio)polymers by utilizing active agents.