The effect of hydrostatic pressure on S-layer-supported lipid membranes

Abstract

We report on the behavior of unsupported and surface layer (S-layer)-supported lipid membranes at the application of a uniform hydrostatic pressure. At a hydrostatic pressure gradient higher than 6 N/m 2, unsupported lipid membranes, independent from which side pressurized and S-layer-supported lipid membranes pressurized from the lipid-faced side revealed a pronounced increase in capacitance. A maximal hydrostatic pressure gradient of 11.0 N/m 2 resulted in an almost doubling of the capacitance of the (composite) membranes. S-layer-supported lipid membranes showed a hysteresis in the capacitance versus pressure plot, indicating that this composite structure required a certain time to reorient when the pressure gradient acting from the lipid-faced side was balanced. By contrast, the S-layer-supported lipid membrane pressurized from the protein-faced side revealed only a minute increase in capacitance ( C/ C 0,max=1.17±0.05), reflecting only minor pressure-induced area expansion. In addition, no hysteresis could be observed, indicating that no rearrangement of the composite membrane occurred. The maximal induced tension was with 4.3±0.2 mN/m, significantly higher than that of unsupported (2.5±0.3 mN/m) and S-layer-supported lipid membranes pressurized from the lipid-faced side (2.6±0.1 mN/m).