State Dependent Blocking Effects on the Alamethicin Pore by Divalent Cations
Free-diffusion theories have been found inadequate for describing a variety of properties of ionic fluxes in biological channels. For this reason deviations from independent movement of ions have been discussed in terms of competitive binding of different ions to discrete sites within a channel. In case of the gramicidin channel, where the inner wall is simply lined by carbonyl oxygens, related phenomena have been described. By way of example, the permeability to alkali cations is blocked in dependence on the concentration of divalent cations to which the gramicidin channel is impermeable.