Coupling between membrane tilt-difference and dilation: a new ``ripple'' instability and multiple crystalline inclusions phases

TL;DR

This paper develops a continuum Landau theory revealing a new ripple phase in membranes due to coupling between membrane tilt and thickness variation, and explores how inclusions influence membrane crystalline phases.

Contribution

It introduces a novel theoretical framework linking membrane tilt and dilation, predicting a ripple instability and complex inclusion-induced crystalline phases.

Findings

Discovery of a ripple micro-structure phase in membranes.

Identification of inclusion types that promote crystalline phases.

Demonstration of coexistence of different lattice spacings at high coupling.

Abstract

A continuum Landau theory for the micro-elasticity of membranes is discussed, which incorporates a coupling between the bilayer thickness variation and the difference in the two monolayers' tilts. This coupling stabilizes a new phase with a rippled micro-structure. Interactions among membrane inclusions combine a dilation-induced attraction and a tilt-difference-induced repulsion that yield 2D crystal phases, with possible coexistence of different lattice spacings for large couplings. Inclusions favoring crystals are those with either a long-convex or a short-concave hydrophobic core.