Lipid exchange enhances geometric pinning in multicomponent membranes on patterned substrates

TL;DR

This study investigates how lipid exchange influences domain pinning and membrane behavior on curved, patterned substrates, revealing that local lipid exchange enhances pinning in curved regions and aids in estimating membrane bending properties.

Contribution

It demonstrates that lipid exchange affects membrane domain pinning and provides a method to estimate bending moduli using complex geometries, advancing understanding of membrane mechanics.

Findings

Lipid exchange enhances liquid disordered phase pinning in curved regions.

The free-energy landscape is shaped by colloid geometry.

Complex geometries improve estimates of membrane bending moduli.

Abstract

Experiments on supported lipid bilayers featuring liquid ordered/disordered domains have shown that the spatial arrangement of the lipid domains and their chemical composition are strongly affected by the curvature of the substrate. Furthermore, theoretical predictions suggest that both these effects are intimately related with the closed topology of the bilayer. In this work, we test this hypothesis by fabricating supported membranes consisting of colloidal particles of various shapes lying on a flat substrate. A single lipid bilayer coats both colloids and substrate, allowing local lipid exchange between them, thus rendering the system thermodynamically open, i.e. able to exchange heat and molecules with an external reservoir in the neighborhood of the colloid. By reconstructing the Gibbs phase diagram for this system, we demonstrate that the free-energy landscape is directly influenced by the geometry of the colloid. In addition, we find that local lipid exchange enhances the pinning of the liquid disordered phase in highly curved regions. This allows us to provide estimates of the bending moduli difference of the domains. Finally, by combining experimental and numerical data, we forecast the outcome of possible experiments on catenoidal and conical necks and show that these geometries could greatly improve the precision of the current estimates of the bending moduli.