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  Structure, ligands and substrate coordination of the oxygen-evolving complex of photosystem II in the S2 state: a combined EPR and DFT study

Lohmiller, T., Krewald, V., Pérez Navarro, M., Retegan, M., Rapatskiy, L., Nowaczyk, M. M., et al. (2014). Structure, ligands and substrate coordination of the oxygen-evolving complex of photosystem II in the S2 state: a combined EPR and DFT study. Physical Chemistry Chemical Physics, 16(24), 11877-11892. doi:10.1039/C3CP55017F.

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 Creators:
Lohmiller, Thomas1, Author              
Krewald, Vera2, Author              
Pérez Navarro, Montserrat1, Author              
Retegan, Marius2, Author              
Rapatskiy, Leonid1, Author              
Nowaczyk, Marc M.3, Author
Boussac, Alain4, Author
Neese, Frank2, Author              
Lubitz, Wolfgang1, Author              
Pantazis, Dimitrios A.2, Author              
Cox, Nicholas1, Author              
Affiliations:
1Research Department Lubitz, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023873              
2Research Department Neese, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023886              
3Ruhr-University Bochum , Universitätsstrasse 150, D-44780 Bochum, Germany, ou_persistent22              
4iBiTec-S, SB2SM, UMR 8221, CEA Saclay, 91191 Gif-sur-Yvette, France, ou_persistent22              

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 Abstract: The S2 state of the oxygen-evolving complex of photosystem II, which consists of a Mn4O5Ca cofactor, is EPR-active, typically displaying a multiline signal, which arises from a ground spin state of total spin ST = 1/2. The precise appearance of the signal varies amongst different photosynthetic species, preparation and solvent conditions/compositions. Over the past five years, using the model species Thermosynechococcus elongatus, we have examined modifications that induce changes in the multiline signal, i.e. Ca2+/Sr2+-substitution and the binding of ammonia, to ascertain how structural perturbations of the cluster are reflected in its magnetic/electronic properties. This refined analysis, which now includes high-field (W-band) data, demonstrates that the electronic structure of the S2 state is essentially invariant to these modifications. This assessment is based on spectroscopies that examine the metal centres themselves (EPR, 55Mn-ENDOR) and their first coordination sphere ligands (14N/15N- and 17O-ESEEM, -HYSCORE and -EDNMR). In addition, extended quantum mechanical models from broken-symmetry DFT now reproduce all EPR, 55Mn and 14N experimental magnetic observables, with the inclusion of second coordination sphere ligands being crucial for accurately describing the interaction of NH3 with the Mn tetramer. These results support a mechanism of multiline heterogeneity reported for species differences and the effect of methanol [Biochim. Biophys. Acta, Bioenerg., 2011, 1807, 829], involving small changes in the magnetic connectivity of the solvent accessible outer MnA4 to the cuboidal unit Mn3O3Ca, resulting in predictable changes of the measured effective 55Mn hyperfine tensors. Sr2+ and NH3 replacement both affect the observed 17O-EDNMR signal envelope supporting the assignment of O5 as the exchangeable μ-oxo bridge and it acting as the first site of substrate inclusion.

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Language(s): eng - English
 Dates: 2013-11-282014-01-312014-06-28
 Publication Status: Published in print
 Pages: 16
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1039/C3CP55017F
 Degree: -

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Title: Physical Chemistry Chemical Physics
  Abbreviation : Phys. Chem. Chem. Phys.
Source Genre: Journal
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Publ. Info: Cambridge, England : Royal Society of Chemistry
Pages: - Volume / Issue: 16 (24) Sequence Number: - Start / End Page: 11877 - 11892 Identifier: ISSN: 1463-9076
CoNE: https://pure.mpg.de/cone/journals/resource/954925272413_1