Photosystem II (PSII) is a unique, specialized protein complex that uses light energy to oxidize water, resulting in the release of molecular oxygen into the atmosphere. PSII performs this reaction within a functional unit known as the water-oxidizing complex (WOC) or the oxygen-evolving complex (OEC). The WOC consists of an inorganic manganese-oxygen-calcium core (Mn4OxCa complex) surrounded by a functionally important ligand sphere. Understanding the structure of the WOC and its water-splitting mechanism is not only of academic interest, but is also important for the development of artificial water-splitting catalysts, for which the WOC often serves as a blueprint.
Messinger Johannes 1150 766Although crystal structures are available for PSII, the detailed structure of the WOC cannot be discerned from them, because of specific radiation damage to the Mn4OxCa cluster. We are therefore trying to derive the structure of the water- splitting complex of photosystem II by a combination of biophysical techniques, such as magnetic resonance (EPR, NMR), X-ray spectroscopy, time-resolved mass spectrometry, electrochemistry and quantum mechanical calculations. These experiments are performed within a network of local and international collaborations. Special emphasis is given to the question of how substrate water is coordinated to the Mn4OxCa cluster. Comparative studies on Mn model complexes and genetically modified photosystem II complexes are carried out to guide data interpretation.
In a new second line of experiments, artificial water-splitting and hydrogen-producing catalysts are being studied under various experimental conditions with an electrochemical cell that is directly coupled to a membrane-inlet mass spectrometer. These activity studies will help our understanding of the water-splitting mechanisms and capacities of such artificial catalysts, which is crucial for their improvement. The ultimate goal is the construction of an ‘artificial leaf’ that uses sunlight to split water into O2 and H2
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Publication list

  1. A microstructured p-Si photocathode outcompetes Pt as a counter electrode to hematite in photoelectrochemical water splitting
    Dalton Trans. 2018 Dec 11 [Epub ahead of print]
  2. Photo-electrochemical hydrogen production from neutral phosphate buffer and seawater using micro-structured p-Si photo-electrodes functionalized by solution-based methods
    SUSTAINABLE ENERGY & FUELS 2018, 2(19):2215-2223
  3. Crystal Structure and Functional Characterization of Photosystem II-Associated Carbonic Anhydrase CAH3 in Chlamydomonas reinhardtii
    Plant Physiol. 2015, 167(3):950-62
  4. Mobile hydrogen carbonate acts as proton acceptor in photosynthetic water oxidation
    PNAS 2014, 111(17):6299-6304
  5. Efficiency of photosynthetic water oxidation at ambient and depleted levels of inorganic carbon
    Photosynth Res. 2013; 117(1-3):401-12
  6. Burén S, Ortega-Villasante C, Blanco-Rivero A, Martinez-Bernardini A, Shutova T, Shevela D, Messinger J, Bako L, Villarejo A, Samuelsson G
    Importance of Post-Translational Modifications for Functionality of a Chloroplast-Localized Carbonic Anhydrase (CAH1) in Arabidopsis thaliana
    PLoS one: 2011 6:e21021
  7. Messinger J, Schroder WP, Renger G
    Structure-Function Relations in Photosystem-Ii - Effects of Temperature and Chaotropic Agents on the Period 4 Oscillation of Flash-Induced Oxygen Evolution
    Biochemistry: 1993 32:7658-7668
  8. Schroder WP, Messinger J, Tremolieres A, Renger G
    On the Effects of Lipase Treatment on the Reaction Pattern of Ps-Ii
    Photosynthesis Research: 1992 34:140-140