Open AccessTHE EFFECT OF REDOX POTENTIAL ON P870 FLUORESCENCE IN REACTION CENTERS FROM Rhodopseudomonas spheroides
Author(s) -
Dan W. Reed,
K. Zankel,
Roderick K. Clayton
Publication year - 1969
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.63.1.42
Subject(s) - redox , photochemistry , absorbance , fluorescence , chemistry , electron transfer , photosynthetic reaction centre , electron acceptor , electron transport chain , rhodopseudomonas palustris , acceptor , titration , bacteriochlorophyll , photosynthesis , inorganic chemistry , biology , optics , biochemistry , physics , chromatography , bacteria , genetics , condensed matter physics
We have prepared photosynthetic reaction centers fromRhodopseudomonas spheroides and have studied the fluorescence of the photochemical electron donor, P870. The yield of this fluorescence rises at low redox potential, presumably because the photochemical electron acceptor becomes reduced and the photochemical utilization of excitation energy is then prevented. The redox titration curve for this increase in the fluorescence has a shape corresponding to the transfer of one electron. The midpoint potential is -0.05 volt, independent of the pH from 6.5 to 8.8. The amplitude of a light-induced absorbance change at 280 nanometers varies with redox potential and shows, at pH 7.5, a midpoint potential of 0.00 volt. These studies indicate that the primary photochemical electron acceptor is not ubiquinone and is not the substance responsible for the absorbance change at 280 nanometers.