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Ammonia binds to the manganese site of the O/sub 2/-evolving complex of photosystem II in the S/sub 2/ state

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00274a027· OSTI ID:5454976
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In this paper, the authors have used low-temperature EPR spectroscopy to monitor the structure and magnetic properties of the Mn site in the presence of NH/sub 3/. They first address the effects on the S/sub 2/ state EPR signal caused by changing the pH from 6.0 to 7.5, since the previous studies were performed at pH 6.0. Next, they demonstrate that binding of NH/sub 3/ to the O/sub 2/-evolving complex causes large changes in the S/sub 2/ state multiline EPR signal trapped after illumination at 0/sup 0/C, indicating that NH/sub 3/ probably binds directly to the MN site in the S/sub 2/ state. However, NH/sub 3/ does not perturb that S/sub 2/ state EPR signal if the S/sub 2/ state is produced by illumination at 210 K, a temperature at which ligand exchange is inefficient. These results demonstrate that coordination of NH/sub 3/ to the Mn site occurs after formation of the S/sub 2/ state. The findings provide direct spectroscopic evidence that the Mn site of the O/sub 2/-evolving complex exchanges ligands, which suggests that the Mn site binds substrate H/sub 2/O molecules during the turnover of the O/sub 2/-evolving complex.
Research Organization:
Yale Univ., New Haven, CT
OSTI ID:
5454976
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:14; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

14 SOLAR ENERGY
140505 -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400500* -- Photochemistry
AMMONIA
CHEMICAL REACTIONS
COMPLEXES
DATA
ELECTRON SPIN RESONANCE
EXPERIMENTAL DATA
FOOD
GYROMAGNETIC RATIO
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
ISOTOPES
LIGHT NUCLEI
LOW TEMPERATURE
MAGNETIC RESONANCE
MANGANESE COMPLEXES
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
PHOTOCHEMICAL REACTIONS
PLANTS
RESONANCE
SPINACH
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
VEGETABLES