title: Collective diffusion model for ion conduction through microscopic channels.
abstract: Ion conduction through microscopic channels is of central importance in both biology and nanotechnology. To better understand the current-voltage (I-V) dependence of ion channels, here we describe and prove a collective diffusion model that quantitatively relates the spontaneous ion permeation at equilibrium to the stationary ionic fluxes driven by small voltages. The model makes it possible to determine the channel conductance in the linear I-V range from equilibrium simulations without the application of a voltage. To validate the theory, we perform molecular-dynamics simulations on two channels-a conical-shaped nanopore and the transmembrane pore of an α-hemolysin-under both equilibrium and nonequilibrium conditions. The simulations reveal substantial couplings between the motions of cations and anions, which are effectively captured by the collective coordinate in the model. Although the two channels exhibit very different linear ranges in the I-V curves, in both cases the channel conductance at small voltages is in reasonable agreement with the prediction from the equilibrium simulation. The simulations also suggest that channel charges, rather than geometric asymmetry, play a more prominent role in current rectification.
authors: Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, USA.
authors: Yingting
authors: Y
authors: Liu
authors: Fangqiang
authors: F
authors: Zhu
mesh_terms: D003198:Computer Simulation; D004058:Diffusion; D029968:Escherichia coli Proteins / Q000378:metabolism; D006460:Hemolysin Proteins / Q000378:metabolism; D015640:Ion Channel Gating; D007473:Ion Channels / Q000378:metabolism*; D017136:Ion Transport; D007477:Ions / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D058608:Nanopores
chemical_list: D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D007473:Ion Channels; D007477:Ions