Theoretical models of conformational transitions and ion conduction in voltage-dependent ion channels: and superionic conduction

摘要

Theoretical studies of the structure and function ofion channels are reviewed, with emphasis on the underlyingphysical phenomena. Nerve and muscle membranes exhibitbehavior interpretable as ferroelectric: Studies show thatconformational transitions in voltage-dependent superionicallyconducting state. The ferroelectric-superionic transition hypothesisis supported by observations of voltage-gated ion conduction,surface charge, hysteresis, pyroelectricity, piezoelectricity,transition temperatures and Curie-Weiss behavior in thesechannels. Macroscopically, the opening of the sodium(Na+)channel appears to involve a moving phase boundary travelingfrom the outer to the inner surface of the axonal membrane.Molecular biology and electrophysiology have provided a partialpicture of the microscopic structure of the Na+ channel,demonstrating a pattern of charged residues that suggests a isproposed to be a ferroelectric liquid crystal component of themembrane, which undergoes a SmC*-SmA transition undercontrol of the voltage across the membrane. The open Na+ channelis proposed to be metalloprotein, in which the permeant ions forman integral part of the channel structure, with ion hopping fromoccupied to vacant sites as the mechanism of selective ionconduction, Ion-exchange reactions that alter the conformation of the molecule.