Abstract
Biological channels are protein molecules that contain a hole and that allow selected ions to pass through a membrane. They provide the mechanism for the control of many physiological functions. For example, a calcium channel selects calcium ions and controls the beating of a heart. We report our Monte Carlo results on model calcium channels. Because of the presence of negatively charged glutamate side chains in the channel, the channel selects calcium ions over sodium ions because of the ability of the divalent calcium ions to deliver twice the charge while occupying the same volume as the monovalent ions in the narrow channel.