MILLIMETER MICROWAVE EFFECT ON ION-TRANSPORT ACROSS LIPID BILAYER-MEMBRANES

The effects of millimeter microwaves in the frequency range of 54-76 G Hz on capacitance and conductance of lipid bilayer membranes (BLM) wer e studied. Some of the membranes were modified by gramicidin A and amp hotericin B or by tetraphenylboron anions (TPhB(.)). The millimeter mi crowaves were pulse-modulated (PW) at repetition rates ranging from 1 to 100 pps, PW at 1000 pps, or unmodulated continuous waves (CW). The maximum output power at the waveguide outlet was 20 mW. It was found t hat CW irradiation decreased the unmodified BLM capacitance by 1.2% +/ - 0.5%. At the same time, membrane current induced by TPhB(.) transpor t increased by 5% +/- 1%. The changes in conductance of ionic channels formed by gramicidin A and amphotericin B were small (0.6% +/- 0.4%). No ''resonance-like'' effects of mm-wave irradiation on membrane capa citance, ionic channel currents, or TPhB(.) transport were detected. A ll changes in membrane capacitance and currents were independent of th e modulation employed and were equivalent to heating by approximately 1.1 degrees C. (C) 1995 Wiley-Liss, Inc.