Structure of two-component lipid membranes on solid support: An x-ray reflectivity study

We report an x-ray reflectivity study of phospholipid membranes deposited on silicon by vesicle fusion. The samples investigated were composed of single phospholipid bilayers as well as two-component lipid bilayer systems with varied charge density. We show that the resolution obtained in the density profile across the bilayer is high enough to distinguish two head-group maxima in the profile if the sample is in the phase coexistence regime. The water layer between the bilayer and silicon is found to depend on the lipid surface charge density.