[Isolation and characterization of photochemical properties of the photosynthetic reaction centers from Rhodopseudomonas shperoides, strain 1760-1].

Photosynthetic reaction centres were isolated from the cells of Rhodopseudomonas spheroides, strain 1760-1, using sodium dodecyl sulphate. The preparations purified by precipitation with ammonium sulphate showed absorbance ratios of A280 : A800=2.1. and A765 : A800 : A870=1 : 2 : 1; about 75% of the bacteriochlorophyll absorbing at 870 nm (P870) were photochemically active. Both absolute and difference "light minus dark" absorption spectra were obtained for the reaction centre suspensions and vacuum-dried films at room and low temperatures. Shift to the longer wavelength of the 870 nm absorption band resulting from temperature lowering suggests the existence of temperature-determined conformations of the bacteriochlorophyll-protein complex of the reaction centres. Characteristic time of an electron transfer from the photoexcited P870 to the primary intermediate of photochemical process as evaluated from the data of pulsed laser fluorometry of the reaction centres was found to be (21--15)+/-8 picoseconds. The oxidized P870 dark reduction kinetics dependence on the actinic light intensity gives evidence for the functioning of heterogeneous pool of the secondary electron acceptors in the reaction centre preparations. Filling in of this pool with electrons is decreased under temperature lowering or vacuum drying and its electron capacity is limited under isooctane treatment resulting in ubiquinon extraction. The ability of the reaction centre preparations to catalyze the photochemical oxidation of iminoxyl aromatic radical was demonstrated.