Membrane lateral structure: The influence of immobilized particles on domain size

TL;DR

This study uses Molecular Dynamics simulations to show that immobilized particles in membranes can lead to small lipid domains, explaining differences between model membranes and cell membranes.

Contribution

It demonstrates that static obstacles in membranes cause small domains, confirming and extending previous Monte Carlo studies with detailed Molecular Dynamics simulations.

Findings

Immobilized particles induce small lipid domains.

Domain formation is insensitive to molecular interaction details.

Simulation results align with Monte Carlo models.

Abstract

In experiments on model membranes, a formation of large domains of different lipid composition is readily observed. However, no such phase separation is observed in the membranes of intact cells. Instead, a structure of small transient inhomogeneities called lipid rafts are expected in these systems. One of the numerous attempts to explain small domains refers to the coupling of the membrane to its surroundings, which leads to the immobilization of some of the membrane molecules. These immobilized molecules then act as static obstacles for the remaining mobile ones. We present detailed Molecular Dynamics simulations demonstrating that this can indeed account for small domains. This confirms previous Monte Carlo studies based on simplified models. Furthermore, by directly comparing domain structures obtained using Molecular Dynamics to Monte Carlo simulations of the Ising model, we demonstrate that domain formation in the presence of obstacles is remarkably insensitive to the details of the molecular interactions.