Sensitized Photoinactivation of Gramicidin Channels: Technique and Applications

Abstract

This review is devoted to the analysis of sensitized photoinactivation of ionic channels formed by gramicidin A in bilayer lipid membranes. There has been a long way from the discovery of this phenomenon in 1992 and the first ideas concerning its mechanism to its application for studying the interaction of different agents with modified gramicidins. Measuring transmembrane current transients after a flash of visible light in the presence of a photosensitizer represents a very convenient method of determining rate constants of gramicidin channel formation and dissociation. In the present review, both the advantages and the drawbacks of the photoinactivation technique are compared with those of the conventional approaches, such as single-channel measurements, the voltage-jump technique, and the noise power spectrum analysis. A study of the interaction of charged gramicidin analogues with polyelectrolytes by using the sensitized photoinactivation procedure is described here in detail to demonstrate the wide potencies of this method. In addition, it is shown that the gramicidin channel photoinactivation can also be used for screening of new potent photosensitizers, and for the search of scavengers effectively protecting membrane systems from the attack of reactive oxygen species.