Abstract
We investigate the influence of surface charges on the rupture of black lipid membranes (BLM). Rupture is induced by short electric voltage pulses across the membrane. The average voltage necessary to induce breakdown gives information on the energy barrier of defect formation. The rapid transmembrane voltage decay during rupture allows one to evaluate the kinetics of defect widening. The breakdown voltage is about the same for BLM made of lipids with phosphatidylserine headgroups and for BLM made of lipids with phosphatidylcholine headgroups. Moreover, the breakdown voltage is independent of the ionic strength of the aqueous medium surrounding the BLM. This indicates that the stability of the BLM is not dominated by mutual electrostatic repulsion of the headgroups. However, the breakdown voltage depends on the type of the hydrophobic chains of the lipids. Palmitoyl-oleoyl (PO) membranes require \ensuremath{\sim}100-mV smaller breakdown voltages compared to diphytanoyl (DPh) membranes. Surprisingly, the rupture kinetics depends on the hydrocarbon chains. It was found to be four times faster for DPh than for PO membranes, and independent of the type of headgroup.
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