title: Kinetic approach with ab initio MO method on ionic selectivity and size in sodium channel.
abstract: Three kinds of models for ionic selectivity and size of the filter in sodium channel have been treated by using ab initio molecular orbital (MO) calculations with MINI-3 and MIDI-3* basis sets. A three-components system, HCO2M-H2O (M = Li+, Na+ or K+), is acceptable for describing experimental facts well. Thermochemical parameters obtained from harmonic vibrational analysis with MINI-3 basis sets, for the translocation of the permeant metal cations in the HCO2M-H2O system, are that the activation enthalpies for Li+, Na+ and K+ are 7.0, 6.4 and 23.4 kJ/mol, and also the free energies of activation are 10.6, 1.5 and 19.0 kJ/mol, respectively. These results are qualitatively in good correspondence with experimental facts of the ion selectivity of the channel. One of water molecule was found to have a key role in the translocation of the permeant cations.
authors.affiliation: Department of Chemistry, Faculty of Science, Hiroshima University, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tani
authors.forename: A
authors.initials: A
authors.lastname: Imamura
authors.forename: K
authors.initials: K
authors.lastname: Kanda
mesh_terms: D000818:Animals; D002412:Cations; D004734:Energy Metabolism; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D010100:Oxygen; D015222:Sodium Channels / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D002412:Cations; D015222:Sodium Channels; D010100:Oxygen