Chapter 8 - Single Ion Channels

Abstract

This chapter focuses on the use of single molecule studies on single ion channels. It first reviews results obtained with single molecule fluorescence methods and compares them with single ion channel results. There are relatively few single molecule experiments on ion channels, other than single-channel recording, possibly because of the difficulty of carrying out single molecule experiments in live cells or at least in a fairly intact biological membrane preparation. A major group of studies is the application of single-particle tracking to channels, in which single channels are observed for the purpose of studying their lateral diffusion in the cell membrane and their interaction with the cytoskeleton and specific proteins such as gephyrin. The photobleaching technique has been used for the purpose of counting subunits in ion channels through imaging by total internal reflection fluorescence (TIRF) microscopy of recombinant channel molecules expressed in Xenopusoocytes at low expression density. Furthermore, the chapter describes a stochastic theory that has been developed for the interpretation of single ion channel records and discusses how it might be applied to other sorts of single molecule observations. An example is presented for an analysis of an ion channel mechanism based on single molecule observations. Single molecule techniques are increasingly being applied to ion channels, which raise the hope that they soon will contribute information to complement and enrich that obtained from electrophysiology.