MPI für bioanorganische Chemie / MPI für bioanorganische Chemie |
|Experimental and Computational X-ray Emission Spectroscopy as a Direct Probe of Protonation States in Oxo-Bridged Mn-IV Dimers Relevant to Redox-Active Metalloproteins.|
|Authors:||Lassalle-Kaiser, Benedikt; Boron, Thaddeus T.; Krewald, Vera; Kern, Jan; Beckwith, Martha A.; Delgado-Jaime, Mario Ulises; Schroeder, Henning; Alonso-Mori, Roberto; Nordlund, Dennis; Weng, Tsu-Chien; Sokaras, Dimosthenis; Neese, Frank; Bergmann, Uwe; Yachandra, Vittal K.; DeBeer, Serena; Pecoraro, Vincent L.; Yano, Junko|
|Date of Publication (YYYY-MM-DD):||2013|
|Title of Journal:||Inorganic Chemistry|
|Journal Abbrev.:||Inorg. Chem.|
|Issue / Number:||22|
|Abstract / Description:||The protonation state of oxo bridges in nature is of profound importance for a variety of enzymes, including the Mn4CaO5 cluster of photosystem II and the Mn2O2 cluster in Mn catalase. A set of dinuclear bis-mu-oxo-bridged Mn-IV complexes in different protonation states was studied by K beta emission spectroscopy to form the foundation for unraveling the protonation states in the native complex. The valence-to-core regions (valence-to-core XES) of the spectra show significant changes in intensity and peak position upon protonation. DFT calculations were performed to simulate the valence-to-core XES spectra and to assign the spectral features to specific transitions. The K beta(2,5) peaks arise primarily from the ligand 2p to Mn Is transitions, with a characteristic low energy shoulder appearing upon oxo-bridge protonation. The satellite K beta '' peak provides a more direct signature of the protonation state change, since the transitions originating from the 2s orbitals of protonated and unprotonated mu-oxo bridges dominate this spectral region. The energies of the K beta '' features differ by similar to 3 eV and thus are well resolved in the experimental spectra. Additionally, our work explores the chemical resolution limits of the method, namely, whether a mixed (mu-O)(mu-OH2) motif can be distinguished from a symmetric (mu-OH)(2) one. The results reported here highlight the sensitivity of K beta valence-to-core XES to single protonation state changes of bridging ligands, and form the basis for further studies of oxo-bridged polymetallic complexes and metalloenzyme active sites. In a complementary paper, the results from X-ray absorption spectroscopy of the same Mn-IV dimer series are discussed.|
|External Publication Status:||published|
|Communicated by:||N. N.|
|Affiliations:||MPI für bioanorganische Chemie|
|External Affiliations:||Lassalle-Kaiser, B.; Kern, J.; Schroeder, H.; Yachandra, V.K.; Yano, J.; Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Phys Biosci Div, Berkeley, CA 94720 USA.
Boron, T.T., III; Pecoraro, V.L.; Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA.
Kern, J.; Alonso-Mori, R.; Nordlund, D.; Weng, T.-C.; Sokaras, D.; Bergmann, U.; SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
Beckwith, M.A.; DeBeer, S.; Cornell Univ, Dept Chem & Chem Biol, Ithaca, NY 14853 USA.
|Identifiers:||ISI:000327225900012 [ID No:1] |
ISSN:0020-1669 [ID No:2]
The scope and number of records on eDoc is subject
to the collection policies defined by each institute
- see "info" button in the collection browse view.