Funds are requested to construct a high sensitivity, high time resolution flash spectrophotometer capable of measurements at UV, visible and near IR wavelengths. A flash lamp is used for interrogation of absorption signals, resulting in extremely high optical resolution coupled with nanosecond time resolution. The use of fiber optic guides to direct light into and away from experimental samples allows the instrument to be easily reconfigured to measure fluorescence and luminescence, all of which make use of essentially the same sensitive electronic components. This type of instrument is used often for biophysical studies of photosynthetic material. Accordingly, four of the major and one of the minor users will concentrate on photosynthetic parameters to evaluate models of protein translocation across biological membranes, responses of photosynthetic material to changing light conditions, organization of the photosynthetic electron transport chain, and intracellular communication between chloroplasts and cell surfaces. Proposed uses for instrument not directly related to photosynthesis include determination of the viscosity of model membranes around reconstituted membrane proteins, investigation of the effects of mutations in the phytochrome apoprotein on phytochrome function, and development of sensitive assays for the function of electrogenic ATPases.
