A combined AC-DC method for investigating supported bilayer lipid membranes

The basic electrical parameters of supported bilayer lipid membranes (s-BLMs) are resistance, capacitance, current, and voltage. Experimentally, either alternating current (AC) or direct current (DC) has been used for their measurements. We describe a simple setup for measurements of electrical properties of s-BLMs, using a complementary AC and DC method. The results obtained have demonstrated the usefulness of such an approach for studying s-BLMs. The frequency dependence of resistance and capacitance results obtained on s-BLMs make them possible to compare different published data obtained by AC at different frequencies or DC. In some experiments capacitance increases more sharply with the lowering of frequency. As demonstrated, certain s-BLMs modified by AQS or TCNQ can transfer electrons readily from the bathing solution via the BLM to the supporting Pt surface. The chances for biotechnological applications may be advanced by suitable modifications of s-BLMs. (C) 1997 Elsevier Science S.A.