On the potential variation in the gramicidin channel.

A simple model for the gramicidin ion pore is analyzed in which the potential energy of the ion in the pore can be resolved into three parts: a series of equal potential barriers, the contribution from the applied potential, and a parabolic variation leading to either a potential maximum or a potential minimum at the center of the membrane. For low ion concentrations, the particular case corresponding to a potential minima 2kT below the surface potential predicts experimentally observed behavior.