Nonlinear electrical effects in lipid bilayer membranes. I. Ion injection.

In this and the following papers a theoretical analysis of the current-voltage characteristic of lipid bilayer membranes is presented. In order to explain the observed nonlinearity, three different mechanisms have to be considered: the injection of ions into the membrane, the distortion of the potential energy profile, and the dissociation field (or Wien) effect. In this first part of the paper, the ion injection effect is analyzed. As both the ion concentration and the thickness of the membrane are extremely small, the constant field approximation can be introduced into the Nernst-Planck equations. In this way the general treatment of Bruner can be greatly simplified, so that the solution is obtained in closed form. The result shows that the ion injection effect gives a contribution to the current-voltage characteristic only at low ionic strength (< 10 (3)M) of the aqueous solution.