Liquid-liquid phase transition temperatures increase when lipid bilayers are supported on glass

Membranes made from certain ternary mixtures of lipids can display coexisting liquid phases. In giant unilamellar vesicles, these phases appear as liquid domains which diffuse and coalesce after the vesicle is cooled below its miscibility transition temperature (T-m). Converting vesicles to supported lipid bilayers alters the mobility of the lipids and domains in the bilayer. At the same time, the miscibility transition temperature of the lipid mixture is altered. Here we compare T-m in vesicles and in supported bilayers formed by rupturing the same vesicles onto glass. We determine transition temperatures using fluorescence microscopy, and identify an increase in T-m when it is measured in identical membranes in solution and on a glass surface. We systematically alter the lipid composition of our membranes in order to observe the correlation between membrane composition and variation in T-m.