Fluctuation induced interactions between domains in membranes

TL;DR

This paper investigates how membrane fluctuations induce interactions between lipid domains, revealing conditions that lead to either attraction or repulsion, which can influence domain formation and size in lipid bilayers.

Contribution

It introduces a model showing how membrane fluctuation-induced interactions depend on local bending rigidity variations, affecting lipid domain behavior.

Findings

Effective lipid interactions can be attractive or repulsive depending on membrane properties.

Repulsive interactions can prevent complete phase separation, resulting in finite-sized domains.

Membrane fluctuations significantly influence lipid domain organization.

Abstract

We study a model lipid bilayer composed of a mixture of two incompatible lipid types which have a natural tendency to segregate in the absence of membrane fluctuations. The membrane is mechanically characterized by a local bending rigidity $\kappa(\phi)$ which varies with the average local lipid composition $\phi$. We show, in the case where $\kappa$ varies weakly with $\phi$, that the effective interaction between lipids of the same type can either be everywhere attractive or can have a repulsive component at intermediate distances greater than the typical lipid size. When this interaction has a repulsive component, it can prevent macro-phase separation and lead to separation in mesophases with a finite domain size. This effect could be relevant to certain experimental and numerical observations of mesoscopic domains in such systems.