Photochemistry in the Isolated Photosystem 2 Reaction Centre
The recent isolation of a complex containing the polypeptides D1, D2 and cytochrome b559, confirmed the proposal that D1 and D2 bind the reaction centre components of PS21,2. The complex was shown to be photochemically active by the photoreduction of phaeophytin and a spin polarised triplet was also detected by epr3. The triplet species originates from a radical pair recombination between the oxidised primary donor chlorophyll P680+ and the reduced phaeophytin acceptor I-4.Redox titrations of the reaction centre preparation using the spin polarised triplet signal confirmed the lack of a quinone electron acceptor but suggested that the non-haem iron still present may act as an electron acceptor when oxidised5.
KeywordsReaction Centre Continuous Illumination Scenedesmus Obliquus Redox Titration Zero Field Split Parameter
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