Photosynthetic water oxidation at high O-2 backpressure monitored by delayed chlorophyll fluorescence

Autor(en): Clausen, J
Junge, W 
Dau, H
Haumann, M
Stichwörter: Biochemistry & Molecular Biology; CLUSTER; COMPLEX; DEPENDENCE; II MEMBRANE-PARTICLES; OXYGEN EVOLUTION; PHOTOSYSTEM-II; SPECTROSCOPY; SPINACH; TEMPERATURE
Erscheinungsdatum: 2005
Herausgeber: AMER CHEMICAL SOC
Journal: BIOCHEMISTRY
Volumen: 44
Ausgabe: 38
Startseite: 12775
Seitenende: 12779
Zusammenfassung: 
The atmospheric dioxygen is produced by photosynthetic organisms. This light-driven process culminates in what appears as one step: a four-electron abstraction from two water molecules bound to the Mn4Ca complex of photosystem II. Recently, an intermediate of the O-2-producing reaction sequence was stabilized by elevated oxygen backpressure and detected by UV flash photometry [Clausen, J., and Junge, W. (2004) Nature 430, 480]. We scrutinized its properties by delayed chlorophyll fluorescence measurements. Half-suppression of oxygen evolution was observed at a similar O-2 pressure of 2.3 bar, as previously, now with photosystem II membrane particles from spinach, without artificial electron acceptors, and at a high signal-to-noise ratio. The data are tentatively interpreted as the stabilization of a 2-fold oxidized state of the catalytic center (S-2*) With bound peroxide and its slow conversion into the normal S-2 state by the release of peroxide.
ISSN: 00062960
DOI: 10.1021/bi051183a

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