Fig. 13. An illustration of how the flow of salt through the channel could impart kinetic energy to the wall of the channel and favor the movement of the sensor out of the channel. The sensor is depicted as a strand with bars representing the amino-acid side chains extending into the lumen of the channel. The arrows indicate the direction of flow of the salt and its collision with the extended amino-acid side chains. The upper figure shows the open state and the lower figure the closed state.