Simulation of the effect of an external GHz electric field on the potential energy profile of Ca ions in the selectivity filter of the Ca Ab channel.

Ca channels are transmembrane proteins that mediate and regulate ion fluxes across cell membranes, and they are activated in response to action potentials to allow Ca influx. Since ion channels are composed of charge or polar groups, an external alternating electric field may affect the ion-selective membrane transport and the performance of the channel. In this article, we have investigated the effect of an external GHz electric field on the dynamics of calcium ions in the selectivity filter of the Ca Ab channel. Molecular dynamics (MD) simulations and the potential of mean force (PMF) calculations were carried out, via the umbrella sampling method, to determine the free energy profile of Ca ions in the Ca Ab channels in presence and absence of an external field. Exposing Ca Ab channel to 1, 2, 3, 4, and 5 GHz electric fields increases the depth of the potential energy well and this may result in an increase in the affinity and strength of Ca ions to binding sites in the selectivity filter the channel. This increase of strength of Ca ions binding in the selectivity filter may interrupt the mechanism of Ca ion conduction, and leads to a reduction of Ca ion permeation through the Ca Ab channel.