Relating Binding Affinity to Dynamical Selectivity from Dynamic Monte Carlo Simulations of a Model Calcium Channel

We have performed dynamic Monte Carlo simulations for a model calcium channel and present our results in terms of binding affinity (expressed as the occupancy of the selectivity filter by various ions) and dynamical selectivity (expressed as the flux carried by various ions). We show that the binding affinity of Ca2+ versus Na+ is always larger than the dynamical selectivity because Ca2+ ions are tightly bound to the binding site of the selectivity filter of the channel and, at the same time, their mobility and drift velocity is smaller in this region. We present density and drift velocity profiles of Ca2+ and Na+ in the channel for various mole fractions of Ca2+.