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- Messinger, Johannes, et al.
(författare)
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Photosynthetic O2 evolution
- 2012
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Ingår i: Molecular solar fuels. - : Royal Society of Chemistry. - 9781849733038 - 9781849730341 ; 2012:1, s. 79-88
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Bokkapitel (refereegranskat)abstract
- Oxygen evolution by photosynthetic water oxidation has shaped life on planet Earth. This unique biological reaction may provide important clues for developing artificial devices (‘artificial leaves’) for splitting water into O2 and H2 by visible light. In this chapter, we summarize the latest structural and mechanistic information on photosystem II, its water-oxidizing complex (WOC), and O2 formation from water at its Mn4CaO5 cluster. Structural information on the WOC derived by X-ray crystallography, X-ray spectroscopy, EPR/ENDOR, and theoretical approaches are compared and discussed in detail. After a description of the basic mechanism of water-oxidation (Kok model), our knowledge about the storage of oxidizing equivalents, substrate water-binding, the release of the products O2 and H+, and the energetics of water-oxidation is described. The near electroneutrality of the water-splitting process via coupling of electron and proton transfer steps and the stabilization of the initial light-driven charge separation by spatial separation and heat dissipation are emphasized as important design principles for coupling fast photochemistry with comparatively slow chemical reactions. The chapter concludes with a discussion of recent DFT-based mechanistic proposals for photosynthetic water oxidation, and with an attempt to identify lessons for the design of artificial systems.
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| 2. |
- Dods, Robert, 1989, et al.
(författare)
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CHAPTER 6: Elucidating Ultrafast Structural Motions in Photosynthetic Reaction Centers with XFEL Radiation
- 2017
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Ingår i: RSC Energy and Environment Series. - Cambridge : Royal Society of Chemistry. - 2044-0774. ; , s. 128-140
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Photosynthetic reaction centers are integral membrane proteins found in photosynthetic plants and bacteria and are the work-horses of photosynthesis. Within these proteins, the energy of sunlight is directed to a special pair of closely spaced chlorophyll molecules that become photo-oxidized as an electron is dispelled to the opposite side of the biological membrane. Evolution has optimized the charge separation reactions of photosynthetic reaction centers so as to achieve a remarkably high quantum yield and energy efficiency. Whether or not ultrafast structural changes play any functional role in guiding the primary charge separation reactions of photosynthesis has been debated for two decades but is not yet resolved. Here, we review progress towards visualizing structural changes in photosynthetic reaction centers using synchrotron radiation. We further describe the revolutionary potential of X-ray free electron lasers (XFELs) for shedding new light on ultrafast structural changes in biomolecules. We emphasize milestones towards the goal of observing functionally important ultrafast motions in photosynthetic reaction centers in real time and anticipate that novel high-resolution structural insights are now technically within reach. © The Royal Society of Chemistry 2017.
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