The size dependence of cholate-dialyzed vesicles on phosphatidylcholine concentration.

The size dependence of vesicles prepared by dialysis of cholate from phosphatidylcholine (PC) dispersions has been investigated as a function of lipid concentration (at a constant applied lipid: detergent molar ratio of 0.7). Gel filtration of dialyzed samples produced a symmetrical profile shape, although quasielastic laser light scattering analysis of the fractions revealed an asymmetrical range of sizes about the peak for solutions containing elevated lipid concentrations. Vesicle diameters increased by approximately 20 nm for PC concentrations ranging from 10 to a maximum of 45 mg/ml. This was attributed to mixed micelle sizes being proportional to lipid concentration, since the diameters of vesicles produced from dialysis are determined by mixed micelle sizes. Before commencement of dialysis, mixed micelle sizes are proportional to lipid concentration and, although dialysis causes an increase in mixed micelle sizes, the phase ratios attained are larger for solutions containing elevated lipid concentrations.