Monte Carlo simulations of ionic channel selectivity

Abstract

Monte Carlo simulations have been developed to study the selectivity of ionic channels in biological membranes. The channel is considered to be in either of two possible states: (i) densely packed with ions, the ions moving in single file in one direction, or alternatively, (ii) sparsely packed, where holes could appear at any particular time thereby allowing bidirectional movement of ions. The two models enable us to envisage a quantitative flux of permeable ions in the presence of smaller sized ions, taking into consideration their concentrations in the bulk solutions, the ion-channel interactions and probability with which they fill up the channel. The programs are written in FORTRAN-77 (MS-FORTRAN) for an IBM-compatible personal computer. From the simulation results we observe an enzymatic function of the channel and also note that the smaller sized ions tend to block the movement of permeable ions. The simulations represent a technique for visualization of the factors that decide ionic permeability and help in manipulating their effects with ease and speed which would otherwise involve intricate experimental setups.