Theories of Ion Permeation: A Chaser

The Perspectives on Ion Permeation in the June issue of The Journal of General Physiology provided a unique exposition of contrasting views regarding kinetic rate models, electrodiffusions, Brownian dynamics, and Poisson-Nernst-Planck (PNP). The debate is timely, healthy, and desirable, because recent progress in the determination of the three-dimensional structure of biological ion channels at atomic resolution gives a fresh impetus to efforts directed at understanding the fundamental principles governing ion permeation (Cowan et al. 1992; Chang et al. 1998; Doyle et al. 1998). Theory is expected to play an important role in those efforts, though we are hard pressed to develop a consensus toward specific approaches. A necessary prerequisite for making any global judgement, however, is to understand the significance of the various treatments and how they relate to one another. In my view, there...