Polymer brush-induced depletion interactions and clustering of membrane proteins

TL;DR

This study combines theoretical models and simulations to explore how mobile polymer brushes influence protein interactions and clustering in membranes, revealing non-monotonic depletion effects related to brush size.

Contribution

It introduces a combined theoretical and simulation approach to understand how polymer brush properties affect membrane protein clustering, linking to experimental observations.

Findings

Depletion attraction varies non-monotonically with brush size.

Depletion interaction increases linearly when brush height is less than protein size.

Large protein clusters can form due to brush-induced depletion forces.

Abstract

We investigate the effect of mobile polymer brushes on proteins embedded in biological membranes by employing both Asakura-Oosawa type of theoretical model and coarse-grained molecular dynamics simulations. The brush polymer-induced depletion attraction between proteins changes non-monotonically with the size of brush. The depletion interaction, which is determined by the ratio of protein size to the grafting distance between brush polymers, increases linearly with brush size as long as the polymer brush height is shorter than the protein size. When the brush height exceeds the protein size, however, the depletion attraction among proteins is slightly reduced. We also explore the possibility of brush polymer-induced assembly of a large protein cluster, which can be related to one of many molecular mechanisms underlying recent experimental observations of integrin nanocluster formation and signaling.