Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation

See allHide authors and affiliations

Science  15 Aug 2014:
Vol. 345, Issue 6198, pp. 804-808
DOI: 10.1126/science.1254910

You are currently viewing the abstract.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

Setting the stage for release of oxygen

Plants transform water into the oxygen we breathe using a protein-bound cluster of four manganese (Mn) ions and a calcium ion. Cox et al. now establish the precise electronic structure in that cluster immediately before formation of the O-O bond (see the Perspective by Britt and Oyala). Using the technique of electron paramagnetic resonance spectroscopy, they confirm a hypothesis that all four Mn ions are octahedrally coordinated and in the 4+ oxidation state. Such clues to the efficiency of the photosynthetic process, so essential to life on Earth, may also facilitate the development of artificial waters-plitting catalysts.

Science, this issue p. 804; see also p. 736


The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor.

View Full Text

Stay Connected to Science