The S sub 3 state of photosystem II: Differences between the structure of the manganese complex in the S sub 2 and S sub 3 states determined by X-ray absorption spectroscopy
- Lawrence Berkeley Laboratory, CA (USA)
- Ruhr-Universitaet-Bochum (West Germany)
O{sub 2}-evolving photosystem II (PSII) membranes from spinach have been cryogenically stabilized in the S{sub 3} state of the oxygen-evolving complex. The cryogenic trapping of the S{sub 3} state was achieved using a double-turnover illumination of dark-adapted PSII preparations maintained at 240 K. A double turnover of PSII was accomplished using the high-potential acceptor, Q{sub 400}, which is the high-spin iron of the iron-quinone acceptor complex. EPR spectroscopy was the principal tool establishing the S-state composition and defining the electron-transfer events associated with a double turnover of PSII. The inflection point energy of the Mn X-ray absorption K-edge of PSII preparations poised in the S{sub 3} state is the same as for those poised in the S{sub 2} state. This is surprising in light of the loss of the multiline EPR signal upon advancing to the S{sub 3} state. This indicates that the oxidative equivalent stored within the oxygen-evolving complex (OEC) during this transition resides on another intermediate donor which must be very close to the manganese complex. An analysis of the Mn extended x-ray absorption fine structure (EXAFS) of PSII preparations poised in the S{sub 2} and S{sub 3} states indicates that a small structural rearrangement occurs during this photoinduced transition. A detailed comparison of the Mn EXAFS of these two S states with the EXAFS of four multinuclear {mu}-oxo-bridged manganese compounds indicates that the photosynthetic manganese site most probably consists of a pair of binuclear di-{mu}-oxo-bridged manganese structures.
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6710223
- Journal Information:
- Biochemistry; (USA), Vol. 29:2; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
PHOTOSYNTHETIC MEMBRANES
MOLECULAR STRUCTURE
PHOTOSYNTHETIC REACTION CENTERS
X-RAY SPECTROSCOPY
ABSORPTION SPECTROSCOPY
ELECTRON SPIN RESONANCE
FINE STRUCTURE
MANGANESE COMPLEXES
OXYGEN
SPINACH
COMPLEXES
ELEMENTS
FOOD
MAGNETIC RESONANCE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MEMBRANES
NONMETALS
PLANTS
RESONANCE
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VEGETABLES
550200* - Biochemistry
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)
400101 - Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures