Displacement currents in lipid bilayer membranes

The processes of charge redistribution in phospholipid bilayer membranes have been examined by voltage clamping. Different types of phospholipids dissolved in n-decane were used as membranes and the membranes were made conducting by adding ionophores. The relaxation processes were found to be composed of at least two exponential decays of which the fast process can be explained in terms of a charge redistribution between the surface layers and the interior of the membrane, following the step in potential. The effect on this of varying the lipid composition, the external solution conditions and the applied potential are described in terms of changes in the capacitance CP and the resistance RP of the surface layers. A model in which a structural rearrangement of the lipid polar groups is responsible for the observed changes in CP and RP is also discussed.