[Electron acceptors in photosynthetic reaction centers from Rhodopseudomonas spheroides]

Using optical differential spectroscopy and EPR, a parallel study of light-induced electron transfer between the primary (X1) and secondary (X2) quinone-like acceptors in the preparations of reaction centers (RC) isolated from bacterial chromatophore membranes with sodium dodecyl sulfate was carried out. The data from direct measurements of the rate constant temperature dependence for the interaction between light-reduced X1 and X2 (KX1X2) are in good agreement with the data calculated from the kinetic analysis of dark reduction of photooxidized bacteriochlorophyll RC on the acceptors X1 and X2 (KX1X2 = 2.10(-1)S at 20 degrees; Ea = 11,8 kcal.mol-1 within the temperature range of 20 degrees-- -20 degrees). This evidence proves the efficiency of the previously used approach /1, 2/ for the evaluation of the X1-X2 interaction. The method proposed was used for a kinetic analysis of a low-temperature electron transfer from X1 to X2 in RC isolated with lauryldimethylaminoxide (KX1X2 = 2,3.10(2) S-1 at 20 degrees; Ea = 5,5 kcal.mol-1 within the temperature range of 10 degrees-- --70 degrees).