When their environment gets high in hydrochloric acid, bacteria must protect themselves from chloride ions leaking into the cells. Some bacteria rely on so-called ClC chloride channels to quickly evacuate these ions without letting other small particles pass through. A recent paper investigates the mechanism of chloride transport in a ClC channel from the bacterium E. coli. By means of computer simulations using NAMD, researchers visualized the pathway taken by chloride ions as they pass through the channel and identified how the channel's protein architecture optimizes ion conduction. The relevant architectural features have also been observed in aquaporin water channels (see November 2003 highlight) and the potassium ion channel, but are rarely seen in other proteins. The new discovery demonstrates how much computer simulations are contributing to the emerging picture of life's membrane channel design that is critical for functions of biological cells ranging from the maintenance of our body's hydration to electrical signaling in the brain.