The Role of Bilayer Tilt Difference in Equilibrium Membrane Shapes

TL;DR

This paper investigates how the tilt difference between bilayer monolayers influences membrane shape, revealing its role in phase stability, symmetry breaking, and introducing a new length scale into membrane elastic theory.

Contribution

It introduces the concept that tilt difference acts as a key factor in membrane shape transitions and symmetry breaking, expanding the understanding of membrane elastic properties.

Findings

Tilt difference can drive membrane shape instabilities.

It introduces a length scale into elastic membrane theory.

It explains spontaneous inversion symmetry breaking in membranes.

Abstract

Lipid bilayer membranes below their main transition have two tilt order parameters, corresponding to the two monolayers. These two tilts may be strongly coupled to membrane shape but only weakly coupled to each other. We discuss some implications of this observation for rippled and saddle phases, bilayer tubules, and bicontinuous phases. Tilt difference introduces a length scale into the elastic theory of tilted fluid membranes. It can drive an instability of the flat phase; it also provides a simple mechanism for the spontaneous breaking of inversion symmetry seen in some recent experiments.