Correlated diffusion of membrane proteins and their effect on membrane viscosity

TL;DR

This paper extends membrane hydrodynamics theory to include correlated protein motion, revealing how protein concentration influences membrane response and diffusion behavior, with implications for understanding membrane viscosity effects.

Contribution

It introduces a modified Saffman theory that accounts for protein correlations and concentration effects on membrane viscosity and diffusion.

Findings

Transverse coupling increases with protein concentration.

Longitudinal coupling remains concentration-independent at large separations.

Membrane viscosity sets the characteristic length scale for membrane response.

Abstract

We extend the Saffman theory of membrane hydrodynamics to account for the correlated motion of membrane proteins, along with the effect of protein concentration on that correlation and on the response of the membrane to stresses. Expressions for the coupling diffusion coefficients of protein pairs and their concentration dependence are derived in the limit of small protein size relative to the inter-protein separation. The additional role of membrane viscosity as determining the characteristic length scale for membrane response leads to unusual concentration effects at large separation -- the transverse coupling increases with protein concentration, whereas the longitudinal one becomes concentration-independent.