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Abstract

The surface potential of biological membranes seems to have influence on the ion transport across the membranes (Frankenhaeuser and Hodgkin, 1957). Changing it also changes the voltage drop across the membrane and therefore alters the field sensed by the transport protein. This will influence the voltage dependent gating of membrane channels (for survey see Hille, 1985). In literature a difference between specific charges at the channel entrance and a charge distribution in the membrane surface mainly created by the lipids is made. The theoretical treatment based on electrostatics by Debye and Hückel, Gouy, Chapman and Stern provide the experimentalist with useful equations to compare with their data. Since it is known that the biological membranes consist of a lipid bilayer into which proteins are embedded (Singer, 1972), the artificial bilayer – invented by P. Müller and coworkers in 1963 (Müller et al., 1963) provides the model system for testing the predictions based on a physical concept applied to biology (for review see McLaughlin, 1977). This article shows the influence of a discrete negative charge on the ion transport through a channel formed by a gramicidin derivative in an artificial bilayer. But before this a survey of the gramicidin in bi1ayers will be given followed by a short description of other bilayer experiments that have been designed to study the influence of charges on the ion transport through the gramicidin channel.