Physiological and Pharmacological Manipulations with Light Flashes

In the experiments described here, a physiological measurement is made while photochemical procedures are employed to alter (a) the concentration of a ligand near membranes or proteins or (b) the structure of the -receptor complexes. Because photochemical reactions often provide the quickest way to produce such chemical perturbations, we emphasize the kinetic information that such experiments have yielded. This information requires a suitably rapid physiological measurement, usually electrical or optical one. The results often complement those obtained with other kinds of kinetic investigation (iontophoretic application of drugs, stopped-flow mixing, temperature jump, etc). Pharmacological manipulations with light flashes are especially useful for biological systems cannot be flowed, for instance membranes under electro-physiological investigation or solutions at very low temperatures.