Kinetic approach with ab initio MO method on ionic selectivity and size in sodium channel.
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.
Tani
S
S
Department of Chemistry, Faculty of Science, Hiroshima University, Japan.
Imamura
A
A
Kanda
K
K
D000818:Animals; D002412:Cations; D004734:Energy Metabolism; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D010100:Oxygen; D015222:Sodium Channels / Q000378:metabolism*; D013816:Thermodynamics
D002412:Cations; D015222:Sodium Channels; D010100:Oxygen