Correlated lateral phase separations in stacks of lipid membranes

TL;DR

This paper models phase separation in stacked lipid membranes using a 3D Ising model, revealing that inter-layer interactions induce continuous columnar structures and accelerate phase separation dynamics.

Contribution

It introduces a stacked Ising spin model to study correlated phase separation in lipid bilayers, highlighting the effects of inter-layer interactions on structure and dynamics.

Findings

Inter-layer correlations lead to continuous columnar structures.

Increased inter-layer interaction accelerates phase separation.

The system exhibits a crossover from 2D to 3D behavior.

Abstract

Motivated by the experimental study of Tayebi et al. [Nature Mater. 11, 1074 (2012)] on phase separation of stacked multi-component lipid bilayers, we propose a model composed of stacked two-dimensional Ising spins. We study both its static and dynamical features using Monte Carlo simulations with Kawasaki spin exchange dynamics that conserves the order parameter. We show that at thermodynamical equilibrium, due to strong inter-layer correlations, the system forms a continuous columnar structure for any finite interaction across adjacent layers. Furthermore, the phase separation shows a faster dynamics as the inter-layer interaction is increased. This temporal behavior is mainly due to an effective deeper temperature quench because of the larger value of the critical temperature, $T_{\rm c}$, for larger inter-layer interaction. When the temperature ratio, $T/T_{\rm c}$, is kept fixed, the temporal growth exponent does not increase and even slightly decreases as function of the increased inter-layer interaction, as the system crosses-over from two to three dimensions.