Simulation of the selectivity of a calcium channel

Our recent simulations of the selectivity of the filter of a calcium channel are reported and discussed briefly. The model calcium filter that is used is a smooth cylinder embedded in a membrane with smooth surfaces. The four glutamate side chains of the calcium channel filter are modeled as eight half-charged oxygen ions that are confined to remain within the filter but are otherwise mobile. This model filter has a strong preference for calcium ions over sodium ions because of the ability of a calcium ion to deliver twice the charge of a sodium ion while occupying the about same volume and so satisfy local charge neutrality in the confined space of the filter more efficiently.