Active dynamics of charged macromolecules

TL;DR

This paper investigates how active enzyme binding influences the transport, swelling, and diffusivity of charged macromolecules, revealing new scaling behaviors and providing formulas relevant for interpreting light scattering experiments.

Contribution

It introduces a model for active enzyme binding effects on charged macromolecules, deriving a diffusion constant expression and analyzing the impact on macromolecular dynamics.

Findings

Active binding enhances macromolecule diffusivity.

New scaling regime in mean-squared displacement due to active coupling.

Swelling of the macromolecule observed through correlation analysis.

Abstract

We study the role of active coupling on the transport properties of homogeneously charged macromolecules in an infinitely dilute solution. An enzyme becomes actively bound to a segment of the macromolecule, exerting an electrostatic force on it. Eventually, thermal fluctuations cause it to become unbound, introducing active coupling into the system. We study the mean-squared displacement (MSD) and find a new scaling regime compared to the thermal counterpart in the presence of hydrodynamic and segment-segment electrostatic interactions. Furthermore, the study of segment-segment equal-time correlation reveals the swelling of the macromolecule. Further, we derive the concentration equation of the macromolecule with active binding and study how the cooperative diffusivity of the macromolecules get modified by its environment, including the macromolecules itself. It turns out that these active fluctuations enhance the effective diffusivity of the macromolecules. The derived closed-form expression for diffusion constant is pertinent to the accurate interpretation of light scattering data in multi-component systems with binding-unbinding equilibria.