Light-flash physiology with synthetic photosensitive compounds.

This review treats a technique that has proved useful recently in some physiological studies. A process is measured while a light flash is used to manipulate a physiologically important or pharmacologically active photosensitive molecule. Typically such experiments complement more common measurements of 1) equilibrium responses in the same system or 2) relaxations after voltage jumps, rapid mixing, and so on. The chief advantage of the lightflash technique is the speed of the photochemistry and the fact that it can be applied to organized systems, such as muscle fibers and membranes under electrophysiological investigation, that cannot be flowed. Experiments may be classified by the accessible time scales (Table 1), by successful recording techniques (Table 2), and by available molecules (Table 3).