Ion transport and channel transition in biomembranes

Abstract

An ion channel is a macromolecular machinery (NANOMACHINE) which regulates the ionic conduction through biomembranes. The ion channels are fundamental in every thought, every perception, every movement, and every heartbeat. The relevant biological dynamics in mesoscopic level is the overdamped slow dynamics. We present a stochastic model to describe the coupled behaviors of ion transport and channel conformation under an applied (trans)membrane potential. We apply our general theoretical formulae to an analytically tractable model of channel with a deep binding site which interacts with the permeant ions electrostatically or entropically. The interaction is found to be modulated by the ionic occupancy which is enhanced by the membrane potential. Above a critical interaction strength or a membrane potential, the interaction gives rise to an emergence of a new conductance state, via a channel conformational transition. This is the self-organization generic to strongly coupled stochastic processes. (C) 2002 Published by Elsevier Science B.V.