The resealing process of lipid bilayers after reversible electrical breakdown

The resealing process of lipid bilayer membranes after reversible electrical breakdown was investigated using two voltage pulses switched on together. Electrical breakdown of the membranes was induced with a voltage pulse of high intensity and short duration. The time course of the change in membrane conductance after the application of the high (short) voltage pulse was measured with a longer voltage pulse of low amplitude. The decrease in membrane conductance during the resealing process could be fitted to a single exponential curve with a time constant of 10--2 micros in the temperature range between 2 and 20 degrees C. The activation energy for this exponential decay process was found to be about 50 kJ/mol, which might indicate a diffusion process. Above 25 degrees C the resealing process is controlled by two exponential processes. The data obtained for the time course of the resealing process can be explained in terms of pore formation in the membrane in response to the high electrical field strength. A radius of about 4 nm is calculated for the initial pore size. From the assumed exponential change of the pore area with progressive resealing time a diffusion constant of 10(-8) cm2/s for lateral lipid diffusion can be estimated.