Pattern formation of phase-separated lipid domains in bilayer membranes

TL;DR

This paper presents a coupled elastic and phase separation model to explain lipid domain patterns in bilayer membranes, aligning with experimental observations and predicting new behaviors like non-monotonic domain size dependence.

Contribution

It introduces a comprehensive theory combining membrane elasticity and lipid phase separation, explaining observed patterns and predicting novel effects.

Findings

Pattern size depends non-monotonically on osmotic pressure

Membrane elasticity influences lipid domain morphology

Hysteresis observed in pattern formation upon stimuli cycling

Abstract

Giant unilamellar vesicles (GUVs) composed of as few as three lipid species can phase separate into small-scale lipid domains with stripes and dots patterns. These patterns have been experimentally characterized in terms of how their size and morphology depend on temperature, membrane composition, and surface tension, which revealed inconsistencies with existing theoretical models. Here, we demonstrate that the experiments can be explained with a theory that considers both the elastic deformation of the membrane and the phase separation of lipids, which are coupled by a preferred bilayer curvature. We combine analytical and numerical approaches to elucidate how characteristic pattern size and morphology emerge from these interactions. The results agree with existing experiments and offer testable predictions such as non-monotonic dependence of the domain size on osmotic pressure and pattern hysteresis upon cycling external stimuli. These predictions motivate new directions for understanding the spatial patterning and organization mechanisms of biological membranes.