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DELAYED FLUORESCENCE AND THE REVERSAL OF PRIMARY PHOTOCHEMISTRY IN RHODOPSEUDOMONAS VIRIDIS
Author(s) -
Fleischman Darrell
Publication year - 1974
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1974.tb06474.x
Subject(s) - fluorescence , photochemistry , quantum yield , chemistry , dcmu , photosynthetic reaction centre , annihilation , yield (engineering) , photosynthesis , electron transfer , photosystem ii , materials science , physics , optics , biochemistry , quantum mechanics , metallurgy
— Delayed fluorescence from chromatophores of the photosynthetic bacterium Rhodopseudomonas viridis was measured at temperatures below 0°C. A component with a decay half‐time of about 7 ms was found. Its intensity was directly proportional to the number of reaction centers in the P985 + ·A ‐ state. During prolonged illumination it faded as electrons moved forward along the electron transport chain from the primary acceptor, A, (P985 + ·A ‐ →P985 + ·A), and its decay in the dark paralleled the disappearence of the P985 + electron paramagnetic resonance absorption. The data suggest that this component of delayed fluorescence results from a direct reversal of the primary light reaction. While the rate of the P985 + middot;A ‐ →P985·A reaction was almost independent of temperature, delayed fluorescence intensity displayed an apparent activation energy of 0°2 eV. It is concluded that the P985 + ·A ‐ →P985·A reaction proceeds by parallel radiative and nonradiative routes. The direct proportionality between delayed fluorescence and the concentration of P985 + ·A ‐ pairs seems to preclude an involvement of triplet‐triplet annihilation or dependence of delayed fluorescence upon the variable prompt fluorescence yield.