A novel rate theory approach to transport in ion channels

We present a novel rate theory based on the notions of splitting probability and mean first passage time to describe conduction of single ions in narrow, effectively 1D membrane channels. In contrast to traditional approaches such as transition state theory or Kramers theory, transitions between different conduction states in our model are governed ?y rates which depend on the full geometry of the potential of mean force (PMF) resulting from the superposition of an equilibrium free energy profile and a transmembrane potential induced by a nonequilibrium constraint. If a detailed theoretical PMF is available (e.g. from atomistic molecular dynamics simulations), it can be used to compute characteristic conductance curves in the framework of our model, thereby bridging the gap between the atomistic and the mesoscopic level of description. Explicit analytic solutions for the rates, the ion flux and the associated electric current can be obtained by approximating the actual PMF by a piecewise linear potential. © 2009 American Institute of Physics.