INTERACTION, LIPID EXCHANGE, AND EFFECT OF VESICLE SIZE IN SYSTEMS OFOPPOSITELY CHARGED VESICLES

The interactions between charged unilamellar vesicles of different siz e prepared from mixtures of egg lecithin (EPC(1)), cholesterol, and a charged component, either stearylamine or dicetyl phosphate, were inve stigated. Several techniques, i.e. fluorescence spectroscopy, Cs-133-N MR, light scattering measurements, and electron and optical microscopi es in dilute aqueous solutions, provided evidence that vesicles bearin g opposite charges interact via contact followed by lipid exchange; th e progressive charge neutralization is shown by Cs-133-NMR to occur wi thout fusion of vesicle internal pools. Vesicle size determines as div erse features as contact duration, extent of lipid exchange, and final distribution of surface charge among the vesicle mixture.