Voltage-induce capacitance relaxation of lipid bilayer membranes. Effects of membrane composition.

The specific capacity of black lipid membranes of different phospholipids dissolved in n-alkanes was investigated. The hydrocarbon thickness of these membranes, as calculated from the electric capacity with a dielectric constant of 2.1, was in most cases close to 5 nm. It was found that the specific capacity is not constant with time after blackening. It shows a linear time dependence characteristic for each lipid/solvent system. The influence of a transmembrane potential on the capacity of the membranes was measured. It was shown that the extent of the capacity change, obtained 10 s after applying a voltage, was strongly dependent on the lipid composition as well as the solvent content of the membranes. The capacity change of the membranes seems to be caused mainly by a thickness change and not by an area increase of the membranes.