How accurately can extended X-ray absorption spectra be predicted from first principles? Implications for modeling the oxygen-evolving complex in photosystem II

Martha A. Beckwith, William Ames, Fernando D. Vila, Vera Krewald, Dimitrios A. Pantazis, Claire Mantel, Jacques Pécaut, Marcello Gennari, Carole Duboc, Marie Noëlle Collomb, Junko Yano, John J. Rehr, Frank Neese, Serena Debeer

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

First principle calculations of extended X-ray absorption fine structure (EXAFS) data have seen widespread use in bioinorganic chemistry, perhaps most notably for modeling the Mn4Ca site in the oxygen evolving complex (OEC) of photosystem II (PSII). The logic implied by the calculations rests on the assumption that it is possible to a priori predict an accurate EXAFS spectrum provided that the underlying geometric structure is correct. The present study investigates the extent to which this is possible using state of the art EXAFS theory. The FEFF program is used to evaluate the ability of a multiple scattering-based approach to directly calculate the EXAFS spectrum of crystallographically defined model complexes. The results of these parameter free predictions are compared with the more traditional approach of fitting FEFF calculated spectra to experimental data. A series of seven crystallographically characterized Mn monomers and dimers is used as a test set. The largest deviations between the FEFF calculated EXAFS spectra and the experimental EXAFS spectra arise from the amplitudes. The amplitude errors result from a combination of errors in calculated S02 and Debye-Waller values as well as uncertainties in background subtraction. Additional errors may be attributed to structural parameters, particularly in cases where reliable high-resolution crystal structures are not available. Based on these investigations, the strengths and weaknesses of using first-principle EXAFS calculations as a predictive tool are discussed. We demonstrate that a range of DFT optimized structures of the OEC may all be considered consistent with experimental EXAFS data and that caution must be exercised when using EXAFS data to obtain topological arrangements of complex clusters.

Original languageEnglish
Pages (from-to)12815-12834
Number of pages20
JournalJournal of the American Chemical Society
Volume137
Issue number40
Early online date29 Sep 2015
DOIs
Publication statusPublished - 14 Oct 2015

Fingerprint Dive into the research topics of 'How accurately can extended X-ray absorption spectra be predicted from first principles? Implications for modeling the oxygen-evolving complex in photosystem II'. Together they form a unique fingerprint.

  • Cite this

    Beckwith, M. A., Ames, W., Vila, F. D., Krewald, V., Pantazis, D. A., Mantel, C., Pécaut, J., Gennari, M., Duboc, C., Collomb, M. N., Yano, J., Rehr, J. J., Neese, F., & Debeer, S. (2015). How accurately can extended X-ray absorption spectra be predicted from first principles? Implications for modeling the oxygen-evolving complex in photosystem II. Journal of the American Chemical Society, 137(40), 12815-12834. https://doi.org/10.1021/jacs.5b00783