Bioelectrochemistry and Bioenergetics, 12 (1984) 393-404 A section of J. Electrounal. Chem., and constituting Vol. 173 (1984) Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands 393 zyxwvutsrqpon 637-THE ELECTRICAL CAPACITANCE OF BILAYER MEMBRANES THE CONTRIBUTION OF TRANSIENT AQUEOUS PORES l JAMES C. WEAVER **, KEVIN T. POWELL and ROBERT A. MINTZER l ** Harvard- MIT Division of Health Sciences and Technology, Cambridge, MA 02139 (U.S.A.) HA0 LING * Departments of Electrical Engineering and Computer Science, and Physics, MIT, Cambridge, MA 02139 (U.S.A.) STEVEN R. SLOAN ** Departments of Electrical Engineering and Computer Science, and Biologv, MIT, Cambridge, MA 02139 (U.S.A.) (Revised manuscript received March 16th 1984) SUMMARY Experiments of others have demonstrated that the electrical capacitance of artificial bilayer mem- branes has a transmembrane potential dependence of the form Elsewhere it is shown that a large population of transient aqueous pores in a bilayer can explain both reversible electrical breakdown and electrically assisted destructive rupture. The population of pores is attributed to thermal fluctuations, such that a bilayer membrane contains many pores which are continually expanding or contracting. Here the contribution of transient aqueous pores to capacitance is calculated. This contribution has the correct transmembrane potential dependence, and can be a significant fraction of the experimental value. An important attribute of such pores is that they are filled with water, not electrolyte. For this reason, the pores in a typical bilayer do not conduct significantly until the transmembrane potential exceeds about 300 mV. Overall, we conclude that the presence of a large population of transient aqueous pores can be consistent with the magnitude and transmembrane potential dependence of the capacitance. l Presented at the 7th International Symposium on Bioelectrochemistry, Stuttgart (F.R.G.), 18-22 July 1983. l * To whom correspondence should be addressed at: 2OA-128, M.I.T., Cambridge, MA 02139, U.S.A. l ** Present address: Department of Physics, University of Chicago, Chicago, IL, U.S.A. * Present address: Department of Electrical Engineering, University of Illinois, Urbana, IL, U.S.A.. ** Present address: Medical School, New York University, New York, NY, U.S.A. 0302-4598/84/$03.00 0 1984 Elsevier Sequoia S.A.