Phase-separation transitions in asymmetric lipid bilayers

TL;DR

This study investigates how asymmetry in lipid composition causes morphological transitions in phase separation within lipid bilayers, leading to nanosized domains stabilized by spontaneous curvature, combining experimental and numerical approaches.

Contribution

It demonstrates the role of local spontaneous curvature in stabilizing micro-phase separation in asymmetric lipid bilayers through combined experimental and modeling evidence.

Findings

Transition from macro- to micro-phase separation observed

Nanosized domains formed via domain scission events

Numerical model aligns with experimental results

Abstract

Morphological transitions of phase separation associated with the asymmetry of lipid composition were investigated using micrometer-sized vesicles of lipid bilayers made from a lipid mixture. The complete macro-phase-separated morphology undergoes a transition to a micro-phase-separation-like morphology via a lorate morphology as a metastable state. The transition leads to the emergence of monodisperse nanosized domains through repeated domain scission events. Moreover, we have numerically confirmed the transitions using the time-dependent Ginzburg-Landau model describing phase separation and the bending elastic membrane, which is quantitatively consistent with experimental results by fixing one free parameter. Our findings suggest that the local spontaneous curvature due to the asymmetric composition plays an essential role in the thermodynamic stabilization of micro-phase separation in lipid bilayers.