Enhanced diffusion, swelling, and slow reconfiguration of a single chain in non-Gaussian active bath.

Abstract

A prime example of a non-equilibrium or active environment is a biological cell. In order to understand in vivo functioning of biomolecules such as proteins and chromatins, a description beyond equilibrium is absolutely necessary. In this context, biomolecules have been modeled as Rouse chains in a Gaussian active bath. However, these non-equilibrium fluctuations in biological cells are non-Gaussian. This motivates us to take a Rouse chain subjected to a series of pulses of force with a finite duration, mimicking the run and tumble motion of a class of microorganisms. Thus by construction, this active force is non-Gaussian. Our analytical calculations show that the mean square displacement (MSD) of the center of mass grows faster and even shows superdiffusive behavior at higher activity. The MSD of a tagged monomer in an active bath also shows superdiffusion at an intermediate time unlike a monomer of a Rouse chain. In the case of a short chain length, reconfiguration is slower and the reconfiguration time of a chain with N monomers scales as Nσ, with σ ≈ 1.6 - 2. In addition, the chain swells. We compare this activity-induced swelling with that of a Rouse chain in a Gaussian active bath. In principle, our predictions can be verified by future single molecule experiments.