Oxidation states of the manganese cluster during the flash-induced S-state cycle of the photosynthetic oxygen-evolving complex

The Mn K-edge x-ray absorption spectra for the pure S states of the tetranuclear Mn cluster of the oxygen-evolving complex of photosystem II during flash-induced S-state cycling have been determined. The relative S-state populations in samples given 0, 1, 2, 3, 4, or 5 flashes were determined from f...

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Published in:Proceedings of the National Academy of Sciences - PNAS 1996-04, Vol.93 (8), p.3335-3340
Main Authors: Roelofs, T.A. (Free University Berlin, Berlin, Germany.), Liang, W, Latimer, M.J, Cinco, R.M, Rompel, A, Andrews, J.C, Sauer, K, Yachandra, V.K, Klein, M.P
Format: Article
Language:English
Subjects:
Absorption spectra
Biochemistry
Biophysics
ESPECTROMETRIA
ESPECTROSCOPIA ESR
Flash spectra
FOTOSISTEMAS
LUMIERE
LUZ
MANGANESE
MANGANESO
Oscillation
OXIDACION
Oxidation
OXIRREDUCION
OXYDATION
OXYDOREDUCTION
Oxygen evolving complex
PHOTOSYSTEME
Physics
SPECTROMETRIE
SPECTROSCOPIE RSE
Spectroscopy
SPINACIA OLERACEA
X ray spectrum
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Summary:The Mn K-edge x-ray absorption spectra for the pure S states of the tetranuclear Mn cluster of the oxygen-evolving complex of photosystem II during flash-induced S-state cycling have been determined. The relative S-state populations in samples given 0, 1, 2, 3, 4, or 5 flashes were determined from fitting the flash-induced electron paramagnetic resonance (EPR) multiline signal oscillation pattern to the Kok model. The edge spectra of samples given 0, 1, 2, or 3 flashes were combined with EPR information to calculate the pure S-state edge spectra. The edge positions (defined as the zero-crossing of the second derivatives) are 6550.1, 6551.7, 6553.5, and 6553.8 eV for S0, S1, S2, and S3, respectively. In addition to the shift in edge position, the S0 leads to S1 and S1 leads to S2 transitions are accompanied by characteristic changes in the shape of the edge, both indicative of Mn oxidation. The edge position shifts very little (0.3 eV) for the S2 leads to S3 transition, and the edge shape shows only subtle changes. We conclude that probably no direct Mn oxidation is involved in this transition. The proposed Mn oxidation state assignments are as follows: S0 (II, III, IV, IV) or (III,III,III, IV), S1 (III, III, IV, IV), S2 (III, IV, IV, IV), S3 (III, IV, IV, IV)
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.93.8.3335