SURFACE-POTENTIALS AND SOLVENT REDISTRIBUTION MAY EXPLAIN THE DEPENDENCE OF ELECTRICAL AND MECHANICAL-PROPERTIES OF SUPPORTED LIPID BILAYERS ON APPLIED POTENTIAL AND BILAYER HISTORY

Using the electrostriction method we have studied the elasticity modul us perpendicular to the membrane plane, E(perpendicular to), and elect rical capacitance, C, of supported bilayer lipid membranes (s-BLM), fo rmed on the freshly cut tip of Ag wire, as a function of d.c. voltage applied to the membrane and time. E(perpendicular to), was found to ch ange non-monotonically with increasing d.c. voltage U-1. These changes depend on the polarity and rate of change of voltage: E(perpendicular to) exhibits a strong maximum at around 200-300 mV (aqueous solution positive with respect to the Ag wire, scan rate 100 mV min(-1)). C dec reases almost monotonically but irregularly under these conditions. An increase in the scan rate leads to a shift toward higher voltages of the value at which the marked changes of E(perpendicular to) and C tak e place. Repeated cyclic scans of U-1 lead to the stepwise stabilizati on of E(perpendicular to) and C, i.e. the changes of these parameters become less pronounced. Analysis of experimental results suggests that solvent redistribution between support-induced inhomogeneities in s-B LM may be the main cause of the observed effects.