Tests of continuum theories as models of ion channels. II. Poisson-Nernst-Planck theory versus brownian dynamics.
We test the validity of the mean-field approximation in Poisson-Nernst-Planck theory by contrasting its predictions with those of Brownian dynamics simulations in schematic cylindrical channels and in a realistic potassium channel. Equivalence of the two theories in bulk situations is demonstrated in a control study. In simple cylindrical channels, considerable differences are found between the two theories with regard to the concentration profiles in the channel and its conductance properties. These differences are at a maximum in narrow channels with a radius smaller than the Debye length and diminish with increasing radius. Convergence occurs when the channel radius is over 2 Debye lengths. These tests unequivocally demonstrate that the mean-field approximation in the Poisson-Nernst-Planck theory breaks down in narrow ion channels that have radii smaller than the Debye length.
Corry
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B
Protein Dynamics Unit, Department of Chemistry, Research School of Physical Sciences, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
Kuyucak
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Chung
S H
SH
D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D007473:Ion Channels / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity; D013816:Thermodynamics
D007473:Ion Channels; D015221:Potassium Channels