Mass changes the diffusion coefficient of particles with ligand-receptor contacts in the overdamped limit

TL;DR

This paper reveals that in overdamped systems, particles with ligand-receptor contacts exhibit a counterintuitive decrease in diffusion speed as their mass increases, supported by simulations and analytical formulas.

Contribution

It introduces a novel analytical model showing mass-dependent diffusion slowdown in ligand-receptor coated particles within the overdamped limit.

Findings

Heavy ligand-receptor particles diffuse slower than lighter ones of the same size.

The effect is potentially observable in micron-scale DNA-coated colloids.

Analytic formula for mass-dependent diffusion coefficient derived.

Abstract

Inertia does not generally affect the long-time diffusion of passive overdamped particles in fluids. Yet a model starting from the Langevin equation predicts a surprising property of particles coated with ligands, that bind reversibly to surface receptors -- heavy particles diffuse more slowly than light ones of the same size. We show this by simulation and by deriving an analytic formula for the mass-dependent diffusion coefficient in the overdamped limit. We estimate the magnitude of this effect for a range of biophysical ligand-receptor systems, and find it is potentially observable for tailored micronscale DNA-coated colloids.