IDENTIFICATION OF CHANNEL MEMBRANE PROCESSES IN BILAYER-LIPID MEMBRANES BY ELECTROCHEMICAL TECHNIQUES

Electrochemical impedance spectroscopy (EIS) was used to investigate t he ionic transport phenomena in multilamellar liposomes (MLV) made of egg yolk phosphatidylcholine (Egg PC), undoped and doped with a low co ncentration of the antibiotic Gramicidin A (GA) in the presence of Na, K+ and Cs+ ions. The membrane/GA interaction can be characterized by the changes observed in the low frequency range of the impedance spec tra. The present EIS data are compared with previous results obtained with black lipid membranes (BLM) and they are discussed taking into ac count the differences and similarities of both model systems, such as time constants and resistance under isotonic, hypertonic and hypotonic conditions, as well as the different methods of antibiotic incorporat ion. (C) 1997 Elsevier Science S.A.