A macroscopically homogeneous lipid phase exhibits leaflet-specific lipid diffusion in a glass-supported lipid bilayer†

Lipid bilayer is a building block of cellular membranes. Understanding the physicochemical properties of a lipid bilayer and their composition dependence is thus inevitable to infer the biological functions of lipids in cellular membranes. Here, we performed leaflet-specific lipid diffusion analysis to study the structural and dynamical properties of lipids on glass-supported lipid bilayers composed of dioleoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine and cholesterol, especially focusing on the regions where a macroscopically homogeneous phase was observed in the ternary phase diagram. The data showed that the interleaflet coupling and the effect of the solid support were highly dependent on the lipid/cholesterol compositions. We also found a distinctive feature of leaflet-specific lipid diffusion in the region near the critical point. This observation was discussed in terms of the nanoscale heterogeneity.