Test of Poisson-Nernst-Planck Theory in Ion Channels

The recent Perspectives on Ion Permeation have brought the debate about the applicability of the Poisson-Nernst-Planck (PNP) theory in ion channels to a sharp focus. Despite the differences in opinion, all sides of the debate agree that the mean field approximation in PNP theory needs to be checked by comparison with a more accurate theory; e.g., Brownian dynamics (BD). Clearly, for such a test to be meaningful it has to be carried out in a three-dimensional (3-D) channel. We have been performing 3-D BD simulations in ion channels for the last few years (Li et al. 1998; Chung et al. 1998, Chung et al. 1999; Hoyles et al. 1998), and have been aware of the differences between the two theories. Therefore, we would like to contribute to the debate by providing a simple test...