Shedding light on membrane proteins.

Membrane proteins are a cell's first line of communication with the world that exists just beyond the plasma membrane. These proteins afford the cell a peek at its external environment, signal the cell to adjust its internal chemistry in response to its surroundings, and ensure that the cell's metabolic state is faithfully coupled to the outside world. Because of their importance in cellular communication, membrane proteins have been the focus of intense study at the functional and structural levels. Here, we describe optical techniques that can either passively monitor or actively control the structural rearrangements that take place as these proteins peek at the outside world. Our focus is on ion channels, but the techniques described can be applied to a host of other proteins.