Letter | Published:

Interaction of cation fluxes in gramicidin A channels in lipid bilayer membranes

Abstract

CLASSICAL studies of potassium movement across the membrane of poisoned giant nerve fibres have shown that passive cationic fluxes through potassium conducting channels are not independent, and suggested a single-file diffusion mechanism1. Interaction of ionic fluxes may provide explanations for important properties of cell membranes, such as non-constancy of ionic selectivity coefficients and blocking effects. On the other hand, the characterisation of the interaction of ionic fluxes may provide information on the mechanism of ion movement across membranes. For model membranes with narrow channels formed by compounds of a known chemical structure such as gramicidin A2–4, where interaction of ionic fluxes and single-file diffusion should be predicted merely by the pore diameter (about 4 Å), no studies of these phenomena have yet been made. We present here results of the determination of interaction between bidirectional Rb+ fluxes in gramicidin A channels which penetrate lipid bilayer membranes.

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