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Characterizing the Electrical Behavior of an Open Channel via the Energy Profile for Ion Permeation

A Prototype Using a Fluctuating Barrier Model for the Acetylcholine Receptor Channel
  • George Eisenman
  • John A. Dani
Part of the Series of the Centro de Estudios Científicos de Santiago book series (SCEC)

Abstract

The fundamental importance of the energy profile in determining the permeability parameters (e.g., selectivity, conductance, and binding) of a channel with classical, static structure has been discussed elsewhere (Eisenman and Horn, 1983). Here we examine what happens to the current-voltage and conductance-concentration behaviors when ä more dynamic view is taken, namely, one in which significant fluctuations in the energy profile can occur on the same time scale as ion translocation. The surfaces of proteins in solution execute thermally excited motion with a root-mean-square amplitude of 1 to 2 Å (Karplus and McCammon, 1983; McCammon, 1984; McCammon and Karplus, 1983). If such motion extended into the pore, it would occur over a significant fraction of the estimated diameter of biological ionic channels and would be expected to perturb significantly the energy profile for ion permeation. Lauger et al. (1980; Lauger, 1984) were the first to extend barrier models of ionic permeation in order to allow for the possibility that the energy profile could fluctuate on the same time scale as ionic migration. They showed that when such fluctuations are coupled to ion translocation, even for a singly occupied channel, they lead to behavior usually associated with multiple occupancy, a conclusion supported by Ciani (1984).

Keywords

Energy Profile Versus Data Fluctuation Rate Microscopic Reversibility Empty Channel 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • George Eisenman
    • 1
  • John A. Dani
    • 1
  1. 1.Department of Physiology, Medical SchoolUniversity of CaliforniaLos AngelesUSA

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