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Density Functional Calculations of Mn-55, N-14 and C-13 Electron Paramagnetic Resonance Parameters Support an Energetically Feasible Model System for the S-2 State of the Oxygen-Evolving Complex of Photosystem II
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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2010 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 16, no 34, 10424-10438 p.Article in journal (Refereed) Published
Abstract [en]

Metal and ligand hyperfine couplings of a previously suggested, energetically feasible Mn4Ca model cluster (SG2009(-1)) for the S, state of the oxygen-evolving complex (OEC) of photosystem II (PSII) have been studied by broken-symmetry density functional methods and compared with other suggested structural and spectroscopic models. This was carried out explicitly for different spin-coupling patterns of the S=(1)/(2) ground state of the Mn-III(Mn-IV)(3) cluster. By applying spin-projection techniques and a scaling of the manganese hyperfine couplings, computation of the hyperfine and nuclear quadrupole coupling parameters allows a direct evaluation of the proposed models in comparison with data obtained from the simulation of EPR. ENDOR, and ESEEM spectra. The computation of Mn-55 hyperfine couplings (HFCs) for SG2009(-1) gives excellent agreement with experiment. However, at the current level of spin projection, the Mn-55 HFCs do not appear sufficiently accurate to distinguish between different structural models. Yet, of all the models studied, SG2009(-1) is the only one with the Mn-III site at the Mn-C center, which is coordinated by histidine (D1-His332). The computed histidine N-14 HFC anisotropy for SG2009(-1) gives much better agreement with ESEEM data than the other models, in which Mn-C is an Mn-IV site, thus supporting the validity of the model. The C-13 HFCs of various carboxylates have been compared with C-13 ENDOR data for PSII preparations with C-13-labelled alanine.

Place, publisher, year, edition, pages
2010. Vol. 16, no 34, 10424-10438 p.
Keyword [en]
cluster compounds, density functional calculations, EPR spectroscopy, photosystem II, structure elucidation
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-51753DOI: 10.1002/chem.201000584ISI: 000282539700021OAI: diva2:386026
authorCount :5Available from: 2011-01-12 Created: 2011-01-12 Last updated: 2011-01-12Bibliographically approved

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Schinzel, SandraSiegbahn, Per E. M.
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Department of PhysicsDepartment of Biochemistry and Biophysics
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