Chiral twist drives raft formation and organization in membranes composed of rod-like particles

TL;DR

This paper demonstrates that chiral twist in membrane particles promotes raft formation and organization, providing a physical mechanism that could explain similar phenomena in biological membranes.

Contribution

It introduces a model of membrane particles as chiral liquid crystals, explaining raft formation and distribution through chiral twist and repulsive interactions.

Findings

Chiral twist promotes finite-sized raft formation.

Chiral interactions mediate repulsion and even distribution.

Model aligns with experimental observations of virus-based colloidal monolayers.

Abstract

Lipid rafts are hypothesized to facilitate protein interaction, tension regulation, and trafficking in biological membranes, but the mechanisms responsible for their formation and maintenance are not clear. Insights into many other condensed matter phenomena have come from colloidal systems, whose micron-scale particles mimic basic properties of atoms and molecules but permit dynamic visualization with single-particle resolution. Recently, experiments showed that bidisperse mixtures of filamentous viruses can self-assemble into colloidal monolayers with thermodynamically stable rafts exhibiting chiral structure and repulsive interactions. We quantitatively explain these observations by modeling the membrane particles as chiral liquid crystals. Chiral twist promotes the formation of finite-sized rafts and mediates a repulsion that distributes them evenly throughout the membrane. Although this system is composed of filamentous viruses whose aggregation is entropically driven by dextran depletants instead of phospholipids and cholesterol with prominent electrostatic interactions, colloidal and biological membranes share many of the same physical symmetries. Chiral twist can contribute to the behavior of both systems and may account for certain stereospecific effects observed in molecular membranes.