EXPERIMENTAL SEARCH FOR COMBINED AC AND DC MAGNETIC-FIELD EFFECTS ON ION CHANNELS

The hypothesis that specific combinations of DC and low frequency AC m agnetic fields at so-called cyclotron-resonance conditions could affec t the transport of ions through ion channels, or alter the kinetics of ion channels (opening and closing rates), has been tested. As a model system, the ion channels formed by gramicidin A incorporated in lipid bilayer membranes were studied. No significant changes in channel con ductance, average lifetime, or formation rate as a function of applied fields could be detected over a wide range of frequencies and field s trengths. Experiments were carried out to measure the time-resolved si ngle-channel events and the average conductances of many-channel event s in the presence of K+ and H+ ions. The channel blocking effect of Ca ++ was also studied. (C) 1993 Wiley-Liss, Inc.