On the physico-chemical basis of voltage-dependent molecular gating mechanisms in biological membranes

The possible nature and theoretical treatment of electric field-induced molecular processes in a membrane are examined. Special attention is given to fairly fast switching phenomena as reflected by asymmetry currents as well as ionic gating in squid axon and similar systems. The apparent charge displacement associated with the underlying mechanisms is argued to be brought about by conformational transitions of integral macromolecular structures. Under these circumstances, voltage changes can actaully control the functional state of membranes by direct interference with conformational equilibria. A basic model is quantitatively discussed and shown to account for certain observed asymmetry currents. Effects due to temperature, pressure, or chemical interactions can be readily described. It is indicated how more complicated voltage-dependent membrane processes may be approached along these lines.