MANIPULATION OF ELECTRIC CHARGE ON VESICLES BY MEANS OF IONIC SURFACTANTS - EFFECTS OF CHARGE ON VESICLE MOBILITY, INTEGRITY, AND LIPID DYNAMICS

A combination of electrophoresis, dynamic light scattering, conductome try: and fluorescence spectroscopy was applied to investigate vesicles (both in the ''solid'' and ''liyuid'' states) that had been imparted with electric charge through the incorporation of ionic amphiphiles. T hese amphiphilic compounds comprised cardiolipin (with two negative ch arges), sodium dodecyl sulfate (with one negative charge), and cetylpy ridinium bromide (with one positive charge). By this means it was disc overed that negative vesicles could be converted into neutral vesicles , and then into positive vesicles, by the addition of a cationic surfa ctant. The amount of cationic surfactant required for the conversion d epended upon the mobility of the surfactant within the bilayer. Vesicl es were found to be capable of absorbing large amounts of surfactant, both cationic and anionic before ultimately disintegrating and releasi ng their contents. Mixtures of cationic and anionic vesicles were able to exchange surfactant, and thereby neutralize each other's charges, without ally concurrent vesicle fusion. This phenomenon is reliable on ly if the vesicles are in the liquid state. Finally, a biphasic exchan ge process was observed in which a surfactant rapidly departs from one bilayer and then enters another, while a fluorescently labeled lipid travels the reverse path only slowly.