Comparison of the structure of the manganese complex in the S/sub 1/ and S/sub 2/ state of the photosynthetic O/sub 2/-evolving complex: an X-ray absorption spectroscopy study
A Mn-containing enzyme complex is involved in the oxidation of H/sub 2/O to O/sub 2/ in algae and higher plants. X-ray absorption spectroscopy is well suited for studying the structure and function of Mn in this enzyme complex. Results of X-ray K-edge and extended X-ray absorption fine structure (EXAFS) studies of Mn in the S/sub 1/ and S/sub 2/ states of the photosynthetic O/sub 2/-evolving complex in photosystem II preparations from spinach are presented in this paper. The S/sub 2/ state was prepared by illumination at 190 K or by illumination at 277 K in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU); these are protocols that limit the photosystem II reaction center to one turnover. Both methods produce an S/sub 2/ state characterized by a multiline electron paramagnetic resonance (EPR) signal. An additional protocol, illumination at 140 K, produces a state characterized by the g = 4.1 EPR signal. The authors have previously observed a shift to higher energy in the X-ray absorption K-edge energy of Mn upon advancement from the dark-adapted S/sub 1/ state to the S/sub 2/ state produced by illumination at 190 K. The Mn K-edge spectrum of the 277 K illuminated sample is similar to that produced at 190 K, indicating that the S/sub 2/ state is similar when produced at 190 or 277 K. A similar edge shape and an edge shift of the same magnitude are seen for the 140 K illuminated sample. These results indicate that the g = 4.1 signal arises from oxidation of the Mn complex and that the structural differences between the species responsible for the g = 4.1 signal and the multiline EPR signal are subtle. They conclude from the edge and EXAFS studies that the light-induced S/sub 1/ to S/sub 2/ transition at 190 K or at 277 K involves a change in the oxidation state of Mn with no EXAFS-detectable change in the coordination of Mn in the O/sub 2/-evolving complex.
- Research Organization:
- Lawrence Berkeley Lab., CA
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5512766
- Journal Information:
- Biochemistry; (United States), Vol. 26:19
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
MANGANESE COMPLEXES
X-RAY SPECTROSCOPY
PHOTOSYNTHETIC MEMBRANES
ABSORPTION SPECTROSCOPY
ELECTROPHORESIS
OXIDATION
OXYGEN
PHOTOSYNTHETIC REACTION CENTERS
SPINACH
SYNCHROTRONS
X-RAY SPECTRA
ACCELERATORS
CHEMICAL REACTIONS
COMPLEXES
CYCLIC ACCELERATORS
ELEMENTS
FOOD
MEMBRANES
NONMETALS
PLANTS
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
VEGETABLES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
140505 - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)