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Manganese: The Oxygen-Evolving Complex and Models

  1. Junko Yano,
  2. Jan Kern

Published Online: 15 SEP 2012

DOI: 10.1002/9781119951438.eibc0121.pub2

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Yano, J. and Kern, J. 2012. Manganese: The Oxygen-Evolving Complex and Models . Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Publication History

  1. Published Online: 15 SEP 2012

Abstract

In this chapter, we give an overview of nature's singular biological process for producing dioxygen by the oxidation of water in photosynthetic organisms. The harnessing of light to accomplish the splitting of water was arguably nature's most successful experiment in biological innovation. It enabled global proliferation of oxygenic photosynthesis and created the biogeochemical cycles of oxygen and carbon on earth. We review the atomic structure of the metalloenzyme, the photosystem II water oxidation complex (PSII-WOC), as revealed by X-ray diffraction and spectroscopic techniques. We describe (i) the electronic and geometric structure of its inorganic core, Mn4CaO5, based upon spectroscopic and diffraction measurements; (ii) the organization of the protein subunits as revealed by X-ray diffraction and the role of select amino acid residues by site-directed mutagenesis; and (iii) the kinetics of the formation of light-induced intermediates, the exchange rates between substrate and free water molecules, the stoichiometry of electron and proton release, and the activation energies to discuss possible mechanisms for photosynthetic water splitting. The chemistry of photosynthetic water splitting is energetically demanding and mechanistically complex. The lessons learned from nature have guided chemists seeking to incorporate these design principles within catalysts suitable for abiotic water splitting. We end with a description of the few synthetic manganese complexes that have been found to produce oxygen from water and discuss the chemical mechanisms by which they appear to function.

Keywords:

  • bioinorganic chemistry;
  • calcium;
  • catalysis;
  • manganese;
  • oxygen evolution;
  • photosynthesis;
  • photosystem II;
  • water splitting