Hierarchy of motions and quasi-particles in a simplified model of potassium channel selectivity filter.
We develop a simplified model of themultiply occupied Kcsa-like selectivityfilter based on the best availablestructural data. The existence of hierarchyof motions in the selectivity filter isshown. Fast fluctuations of the ion-iondistances may be considered adiabaticallydecoupled from the slow diffusive motion ofthe ions' center of masses. The latter canbe considered as a quasi-particle, called aquasi-ion, moving in an effectivepotential. In the Kcsa-like selectivityfilter occupied by three ions the effectivepotential allows free barrier-lessdiffusional motion of the quasi-ions. Theconcept of the quasi-ions performing iontranslocation through the channel may bevital in explaining barrier-less `knock-on' conduction postulated for real channels.
Department of Biophysics, Institute of Physics, Natl. Acad. of Sci. of Ukraine, Prospect Nauki, 46, Kiev 03039 Ukraine.
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Yesylevskyy
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Kharkyanen
Kcsa channel; hierarchy of motions; potassium channel; quasi-particles; selectivity filter