Energetics of Photosystem II Charge Recombination in Acaryochloris marina Studied by Thermoluminescence and Flash Induced Chlorophyll Fluorescence Measurements
Charge recombination characteristics in Photosystem II were studied in whole cells of the chlorophyll d-dominated cyanobacterium, Acaryochloris marina. Thermoluminescence intensity is enhanced 2.5-fold per photosystem II center in Acaryochloris, as compared to the chlorophyll a containing cyanobacterium, Synechocystis 6803. Flash induced chlorophyll fluorescence is retarded or accelerated slightly in the absence or presence of the QB site inhibitor, DCMU, respectively, in Acaryochloris. Mild reduction retarded fluorescence relaxation significantly in Acaryochloris with almost no effect on Synechocystis. The modified charge recombination energetics show that the Em of QA and QB is increased, and the redox gap between P* and P+ Phe− is decreased in Acaryochloris relative to Synechocystis. The free energy span between P and P* is decreased indicating the involvement of chlorophyll d in primary electron donor activity.
KeywordsPhotosystem II electron transfer Acaryochloris marina chlorophyll d
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