Conditions for extreme sensitivity of protein diffusion in membranes to cell environments

TL;DR

This study investigates how protein diffusion in multicomponent lipid membranes near a substrate becomes highly sensitive to environmental conditions, especially near phase separation critical points, due to power-law dependencies.

Contribution

It introduces a nonlinear stochastic Navier-Stokes model that reveals significant environmental sensitivity of protein diffusion near critical points in lipid membranes.

Findings

Diffusion shows power-law dependence on temperature and substrate distance near critical points.

Advective nonlinearity has a minor effect at room temperature.

Diffusion sensitivity is much greater near phase separation critical points.

Abstract

We study protein diffusion in multicomponent lipid membranes close to a rigid substrate separated by a layer of viscous fluid. The large-distance, long-time asymptotics for Brownian motion are calculated using a nonlinear stochastic Navier-Stokes equation including the effect of friction with the substrate. The advective nonlinearity, neglected in previous treatments, gives only a small correction to the renormalized viscosity and diffusion coefficient at room temperature. We find, however, that in realistic multicomponent lipid mixtures, close to a critical point for phase separation, protein diffusion acquires a strong power-law dependence on temperature and the distance to the substrate $H$, making it much more sensitive to cell environment, unlike the logarithmic dependence on $H$ and very small thermal correction away from the critical point.