The effect of light and temperature on the dynamic state of Rhodobacter sphaeroides reaction centers proteins determined from changes in tryptophan fluorescence lifetime and P + Q A - recombination kinetics.

The temperature dependencies of the rate of dark recombination of separated charges between the photoactive bacteriochlorophyll and the primary quinone acceptor (QA) in photosynthetic reaction centers (RCs) of the purple bacteria Rhodobacter sphaeroides (Rb. sphaeroides) were investigated. Measurements were performed in water−glycerol and trehalose environments after freezing to −180 °C in the dark and under actinic light with subsequent heating. Simultaneously, the RC tryptophanyl fluorescence lifetime in the spectral range between 323 and 348 nm was measured under these conditions. A correlation was found between the temperature dependencies of the functional and dynamic parameters of RCs in different solvent mixtures.