We propose to continue our study of electric perforation of cell membranes. Previously we have shown that application of high voltage electric pulses, in microseconds, to an isotonic suspension of erythrocytes introduced aqueous pores of limited size in the red cell membranes. These pores could be resealed at 37 degrees without hemolysis. The resealed cells retained all of the protein contents and carried the entrapped 3H-sucrose in the circulation of laboratory mice with a normal lifetime of 15-20 days. Work will continue in the following areas. 1) Investigate the molecular mechanism and locate specific sites of pore formation: Evidences already indicate 35% occurred at the Na/K ATPase sites. Another 65% needs to be located. 2) Entrap clinically active drugs and use erythrocytes as drug carriers. 3) Develop this technique into a general method for altering the membrane conductances, perturbing the transmembrane potential, and selectively changing the membrane permeability. 4) Study membrane potential mediated active transport, energy transduction e.g., ATP synthesis, and other transmembrane phenomena. These require development of low voltage stimulation techniques, as high voltage leads to irreversible denaturation of channel proteins. We also propose to continue work on thermodynamic and kinetic characterization of various forms of lipid vesicles, lipid binary mixtures, lipid protein complexes. Especially, we will compare physical properties of unilamellar small vesicles, unilamellar large vesicles, and multilamellar liposomes. Our earlier analysis was based on data obtained with liposomes. Now, it apppears that interlayer interactions exist. We also intend to study electrical perforation of the bilayer in unilamellar large vesicles, and channel opening in vesicles incorporated with yeast plasma membrane ATPase. The proposed physical study would yield information on stability and permeability of bilayers, lipid clustering, fusion of vesicles, and is thus important for understanding lipid deposition diseases and biological functions of cell membranes.