Manganese K-edge X-ray absorption spectra of the cyclic S-states in the photosynthetic oxygen-evolving system |
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Authors: | M Kusunoki T Ono T Noguchi Y Inoue H Oyanagi |
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Institution: | (1) Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, 214 Kawasaki, Kanagawa, Japan;(2) Solar Energy Research Group, Institute of Physical and Chemical Research (RIKEN), 351-01 Wako, Saitama, Japan;(3) Electrotechnical Laboratory, 305 Tsukuba, Ibaraki, Japan |
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Abstract: | A set of Mn K-edge XANES spectra due to the redox states S0–S3 of the OEC were determined by constructing a highly-sensitive X-ray detection system for use with physiologically native PS II membranes capable of cycling under a series of saturating laser-flashes. The spectra showed almost parallel upshifts with relatively high K-edge half-height energies given by 6550.9±0.2 eV, 6551.7±0.2 eV, 6552.5±0.2 eV and 6553.6±0.2 eV for the S0, S1, S2 and S3 states, respectively. The successive difference spectra between S0 and S1, S1 and S2, and S2 and S3 states were found to exhibit a similar peak around 6552–6553 eV, indicating that one Mn(III) ion or its direct ligand is univalently oxidized upon each individual S-state transition from S0 to S3. The present data, together with other observations of EPR and pre-edge XANES spectroscopy, suggest that the oxidation state of the Mn cluster undergoes a periodic change; S0: Mn(III,III,III,IV) S1: Mn(III,IV,III,IV) S2: Mn(III,IV,IV,IV) S3: Mn(IV,IV,IV,IV) or Mn(III,IV,IV,IV)·L+ with L being a direct ligand of a Mn(III) ion.Abbreviations Chl
chlorophyll
- D
tyrosine 160 on the D2 protein, an accessory electron donor in PS II
- D+
the oxidized form of D
- EDTA
ethylene-diaminetetraacetic acid
- EPR
electron paramagnetic resonance
- EXAFS
extended X-ray absorption fine structure
- HL
py-2,6-bisbis(2-pyridylmethyl)aminomethyl]-4-methylphenol
- Mes
2-(N-morpholino)ethanesulfonic acid
- N4
py-tris(2-pyridylmethyl)amine
- OEC
oxygen evolving complex
- P680
primary electron donor of PS II
- PS II
Photosystem II
- Q400
a high spin Fe3+ of the iron-quinone acceptor complex in PS II
- SSD
solid state detector
- XAFS
X-ray absorption fine structure
- XANES
X-ray absorption near edge structure |
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Keywords: | manganese cluster oxygen evolution Photosystem II water oxidation XANES |
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