Flash induced XANES spectroscopy for the Ca-depleted Mn-cluster in the photosynthetic O2-evolving enzyme.
Flash-induced changes of the Mn K-edge absorption spectra have been studied in the oxygen-evolving complex depleted of Ca. The Mn K-edge energy for the Ca-depleted S1-state was lower by 1.5 eV than that for the normal S1-state. The K-edge energy upshifted by 1 eV after one flash, indicative of an oxidation of Mn. After two flashes, the K-edge was elevated as well by 0.4 eV, and then reached a steady-state high level after continuous illumination where the K-edge energy was higher by 0.9 eV than that after one flash. The results indicate that the Mn-cluster and/or its direct ligand could be oxidized up to two electrons but further events are blocked.
Ono
T
T
Solar Energy Research Group, Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
Noguchi
T
T
Inoue
Y
Y
Kusunoki
M
M
Yamaguchi
H
H
Oyanagi
H
H
D002118:Calcium / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000032:analysis*; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods
D045322:Photosynthetic Reaction Center Complex Proteins; D008345:Manganese; D010100:Oxygen; D002118:Calcium