Analysis of post-perturbation gating kinetics of single ion channels

Abstract

Analysis of mean dwell-times as a function of the number of channel openings elapsed since a stepwise perturbation in ion-channel kinetics is shown to provide information concerning the topology of the underlying gating mechanism. The difference between the post-perturbation mean dwell-time and the corresponding equilibrium mean is shown to decay as the sum of N g – 1 geometric terms in k , the number of openings since the perturbation, where N g is the minimum number of gateway states in the channel gating mechanism. The method is illustrated by consideration of various simple gating schemes. A modification of the method accommodating the presence of channel inactivation or desensitization is described. Application of the method to a delayed-rectifier type K + channel of NG108-15 cells reveals that N g ≽ 2, consistent with a branched gating mechanism.