Solid domains in lipid vesicles and scars

TL;DR

This paper investigates the energetics and morphology of crystalline domains with defect arrays in lipid vesicles, revealing how scars influence domain stability and shape transitions, with implications for understanding phase separation in biological membranes.

Contribution

It introduces the concept that scars in crystalline domains cause linear growth of stretching energy, explaining the stability of solid domains in lipid bilayers even at small coverages.

Findings

Scars cause linear energy growth with domain size.

Domains transition from caps to stripes as line tension decreases.

Results have implications for particle arrangements on fixed geometries.

Abstract

The free energy of a crystalline domain coexisting with a liquid phase on a spherical vesicle may be approximated by an elastic or stretching energy and a line tension term. The stretching energy generally grows as the area of the domain, while the line tension term grows with its perimeter. We show that if the crystalline domain contains defect arrays consisting of finite length grain boundaries of dislocations (scars) the stretching energy grows linearly with a characteristic length of the crystalline domain. We show that this result is critical to understand the existence of solid domains in lipid-bilayers in the strongly segregated two phase region even for small relative area coverages. The domains evolve from caps to stripes that become thinner as the line tension is decreased. We also discuss the implications of the results for other experimental systems and for the general problem that consists in finding the ground state of a very large number of particles constrained to move on a fixed geometry and interacting with an isotropic potential.