Absence of Mn-centered oxidation in the S(2) --> S(3) transition: implications for the mechanism of photosynthetic water oxidation.
J Am Chem Soc
; 123(32): 7804-20, 2001 Aug 15.
Article
de En
| MEDLINE
| ID: mdl-11493054
ABSTRACT
A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen-evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S(3) --> [S(4)] --> S(0) transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn Kbeta X-ray emission spectroscopy (Kbeta XES) to this problem for the first time. The Kbeta XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S(2) --> S(3) transition, in contrast to the S(0) --> S(1) and S(1) --> S(2) transitions, does not involve a Mn-centered oxidation. On the basis of new structural data from the S(3)-state, manganese mu-oxo bridge radical formation is proposed for the S(2) --> S(3) transition, and three possible mechanisms for the O-O bond formation are presented.
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Photosynthèse
/
Eau
/
Manganèse
Langue:
En
Journal:
J Am Chem Soc
Année:
2001
Type de document:
Article
Pays d'affiliation:
États-Unis d'Amérique