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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Nilsson, Håkan Ames, William M. Pantazis, Dimitrios A. Boussac, Alain Cox, Nicholas Neese, Frank Messinger, Johannes Lubitz, Wolfgang Lohmiller, Thomas Rapatskiy, Leonid Pérez Navarro, Montserrat Nowaczyk, Marc M. |
| Description | Author Affiliation: Pérez Navarro M ( Max-Planck-Institut für Chemische Energiekonversion, D-45470 Mülheim an der Ruhr, Germany.); |
| Abstract | The assignment of the two substrate water sites of the tetra-manganese penta-oxygen calcium $(Mn_{4}O_{5}Ca)$ cluster of photosystem II is essential for the elucidation of the mechanism of biological O-O bond formation and the subsequent design of bio-inspired water-splitting catalysts. We recently demonstrated using pulsed EPR spectroscopy that one of the five oxygen bridges (μ-oxo) exchanges unusually rapidly with bulk water and is thus a likely candidate for one of the substrates. Ammonia, a water analog, was previously shown to bind to the $Mn_{4}O_{5}Ca$ cluster, potentially displacing a water/substrate ligand [Britt RD, et al. (1989) J Am Chem Soc 111(10):3522–3532]. Here we show by a combination of EPR and time-resolved membrane inlet mass spectrometry that the binding of ammonia perturbs the exchangeable μ-oxo bridge without drastically altering the binding/exchange kinetics of the two substrates. In combination with broken-symmetry density functional theory, our results show that (i) the exchangable μ-oxo bridge is O5 {using the labeling of the current crystal structure [Umena Y, et al. (2011) Nature 473(7345):55–60]}; (ii) ammonia displaces a water ligand to the outer manganese $(Mn_{A4}-W1);$ and (iii) as W1 is trans to O5, ammonia binding elongates the $Mn_{A4}-O5$ bond, leading to the perturbation of the μ-oxo bridge resonance and to a small change in the water exchange rates. These experimental results support O-O bond formation between O5 and possibly an oxyl radical as proposed by Siegbahn and exclude W1 as the second substrate water. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 39 |
| Volume Number | 110 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2013-09-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Ammonia Metabolism Manganese Oxygen Photosystem II Protein Complex Solvents Electrons Ligands Magnetic Resonance Spectroscopy Chemistry Spin Labels Research Support, Non-U.S. Gov't Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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