Electrochemistry of Symmetrical Ion Channel: A Three-Dimensional Nernst-Planck- Poisson Model
Here, the stationary behavior is studied of the different symmetrical channels showing complex geometry. The rigid channel wall is assumed to be locally charged. The ion transport is described by the nonequilibrium steady-state solution in cylindrical geometry of the 3DNernst-Planck-Poisson system. The total flux includes drift (convection) and diffusion terms. The solution of the coupled differential drift-diffusion equations is achieved by finite element method. The essential importance of the asymmetry in the potential distribution at the channel ends on the selectivity effect is demonstrated. The model satisfactorily describes the regime of small-to-moderate ionic currents. For various boundary conditions that are key parameters controlling the selectivity of the channel, it allows determining the flow characteristic, calculating the local concentration across the channel showing cylindrical symmetry and potential distribution. The model gives understanding of the mechanism of ion selectivity by channels but it can be also applied to simulate transport in polymer membranes and nanopores which might be useful in designing biosensors and nanodevices.
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