Effect of Average Phospholipid Curvature on Supported Bilayer Formation on Glass by Vesicle Fusion

The adsorption of large unilamellar vesicles composed of various combinations of phosphatidylcholine, phosphatidylethanolamine (PE), monomethyl PE, and dimethyl PE (PE-Me2) onto a glass surface was studied using fluorescence microscopy. The average lipid geometry within the vesicles, described mathematically by the average intrinsic curvature, C0,ave, was methodically altered by changing the lipid ratios to determine the effect of intrinsic curvature on the ability of vesicles to rupture and form a supported lipid bilayer. We show that the ability of vesicles to create fluid planar bilayers is dependent on C0,ave and independent of the identity of the component lipids. When the C0,ave was ∼−0.1 nm−1, the vesicles readily formed supported lipid bilayers with almost full mobility. In contrast, when the C0,ave ranged from ∼−0.2 to ∼−0.3 nm−1, the adsorbed vesicles remained intact upon the surface. The results indicate that the average shape of lipid molecules within a vesicle (C0,ave) is essential for determining kinetically viable reactions that are responsible for global geometric changes.