Although 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
- Cox, N and Messinger, J (2013) Reflections on substrate water and dioxygen formation. Biochim Biophys Acta 1827, 1020-1030.
- Kern, J, et al. (2013) Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature. Science: 340, 491-495.
- Rapatskiy, L, et al. (2012) Detection of the water-binding sites of the oxygen-evolving complex of photosystem II using W-band 17O Electron-Electron Double Resonance-detected NMR spectroscopy. J. Am. Chem. Soc. 134: 16619-16634.
- Shevela, D, et al. (2011) Membrane-inlet mass spectrometry reveals a high driving force for oxygen production by photosystem II. Proc. Natl. Acad. Sci. USA 108: 3602-3607.
- Shevela, D, et al. (2011) Calcium Manganese Oxides as Oxygen Evolution Catalysts: O2 Formation Pathways Indicated by 18O-Labelling Studies. Chem. Eur. J. 17: 5415-5423.