Molecular Perspectives of Monovalent Cation Selective Transmembrane Channels

Abstract

Publisher Summary This chapter discusses three basic structural models for transmembrane channels. The molecular species to be evaluated for its ion transport properties is added directly to the water solution on one or both sides of the membrane, or it is added directly to the lipid solution and its conduction properties are evaluated by means of the electrodes. The value of this approach, and its subsequent refinements, to the development of the understanding of mechanisms of selective ion transport across lipid bilayer membranes cannot be overstated. It is reasonable to expect that substantial hydration energy be gained from molecules in the second coordination shell and beyond because the energy of hydration is four times greater for a divalent cation than for monovalent cations. As a means of overcoming some of the aforementioned limitations while retaining the favorable structural features giving rise to monovalent cation selectivity, a molecular theory of electric-field-dependent channel formation is developed, after the necessary derivation of a more generally applicable conformational concept of cyclic conformations with linear conformational correlates.