CHLORIDE REQUIREMENT IN PHOTOSYSTEM II AND ANION EFFECTS IN THE S2’ STATE OF THE OXYGEN EVOLVING COMPLEX By
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چکیده
The oxygen evolving complex (OEC) of photosystem II (PSII) requires chloride as a critical cofactor. The Cl content of PSII was determined to be 1 Cl/PSII by the AgCl colloid assay. The dissociation constant for Cl in NaCl-washed PSII was determined using the Cl sensitive microelectrode. Two classes of Cl binding sites were found with Kd values of 53 μM and 4.2 mM. The effects of anions on the S2’ oxidation state of the OEC were investigated using electron paramagnetic resonance spectroscopy. It was found that chloride was
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