A stochastic model of conductance transitions in voltage-gated ion channels

We present a statistical physics model to describe the stochastic behavior of ion transport and channel transitions under an applied membrane voltage. To get pertinent ideas we apply our general theoretical scheme to an analytically tractable model of the channel with a deep binding site which interacts with the permeant ions electrostatically. It is found that the interaction is modulated by the average ionic occupancy in the binding site, which is enhanced by the membrane voltage increases. Above a critical voltage, the interaction gives rise to a emergence of a new conducting state along with shift of S4 charge residues in the channel. This exploratory study calls for further investigations to correlate the complex transition behaviors with a variety of ion channels, with parameters in the model, potential energy parameters, voltage, and ionic concentration.