Dec 15, 2000

X-ray spectroscopy-based structure of the Mn cluster and mechanism of photosynthetic oxygen evolution

Biochimica Et Biophysica Acta
John H RobbleeVittal K Yachandra

Abstract

The mechanism by which the Mn-containing oxygen evolving complex (OEC) produces oxygen from water has been of great interest for over 40 years. This review focuses on how X-ray spectroscopy has provided important information about the structure of this Mn complex and its intermediates, or S-states, in the water oxidation cycle. X-ray absorption near-edge structure spectroscopy and high-resolution Mn Kbeta X-ray emission spectroscopy experiments have identified the oxidation states of the Mn in the OEC in each of the intermediate S-states, while extended X-ray absorption fine structure experiments have shown that 2.7 A Mn-Mn di-mu-oxo and 3.3 A Mn-Mn mono-mu-oxo motifs are present in the OEC. X-ray spectroscopy has also been used to probe the two essential cofactors in the OEC, Ca2+ and Cl-, and has shown that Ca2+ is an integral component of the OEC and is proximal to Mn. In addition, dichroism studies on oriented PS II membranes have provided angular information about the Mn-Mn and Mn-Ca vectors. Based on these X-ray spectroscopy data, refined models for the structure of the OEC and a mechanism for oxygen evolution by the OEC are presented.

Mentioned in this Paper

Manganese
Dioxygen
Tissue Membrane
Oxygen Evolving Complex
Plain X-ray
X-ray Spectroscopy
Oxidation
Radiographic Imaging Procedure
Near Edge X-Ray Absorption Fine Structure Spectroscopy
Oxidation-Reduction

About this Paper

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