Theoretical EXAFS studies of a model of the oxygen‐evolving complex of photosystem II obtained with the quantum cluster approach

Abstract

Link to publicationCitation for published version (APA): Li, X., Sproviero, E. M., Ryde, U., Batista, V. S., & Chen, G. (2013). Theoretical EXAFS studies of a model of the oxygen-evolving complex of photosystem II obtained with the quantum cluster approach. International Journal of Quantum Chemistry, 113(4), 474-478. DOI: 10.1002/qua.24143 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ABSTRACTThe oxygen-evolving complex (OEC) of photosystem II is the only natural system that can form O 2 from water and sunlight and it consists of a Mn 4 Ca cluster. In a series of publications, Siegbahn has developed a model of the OEC with the quantum mechanical (QM) cluster approach that is compatible with available crystal structures, able to form O 2 with a reasonable energetic barrier, and has a significantly lower energy than alternative models. In this investigation, we present a method to restrain a QM geometry optimization towards experimental polarized EXAFS data. With this method, we show that the cluster model is compatible with the EXAFS data and we obtain a refined cluster model that is an optimum compromise between QM and polarized EXAFS data.

Theoretical studies of the damage-free S1 structure of the CaMn4O5 cluster in oxygen-evolving complex of photosystem II

“…However, the symmetrybreaking parameter [36]; (2.70-2.33)/2 = 0.19Å, is small, providing the slightly right-elongated quasi-central (C R ) structure in our terminology. Thus the S 1 (C R ) structure revealed by XFEL [21] in Figure 1B is topologically different from the S 1 (R) structure proposed by several groups based on theoretical studies [22,23,[39][40][41][42][43], as shown in Figure 1C. [21] are directly related to the reduction of the Mn-Mn distances (see Table S1) mentioned above.…”

“…The external reduction of the high-valent Mn ions of the CaMn 4 O 5 cluster has been examined by several groups [7,22,23,[39][40][41][42][43] on both experimental and theoretical grounds in relation to the X-ray damage of the high-resolution (3ARC) XRD structure. On the other hand, we have examined the internal and semi-internal reduction [33,36,37] of the CaMn 4 O 5 cluster of OEC of PSII on the basis of the spin density populations, as shown in Table 1.…”

Simulation of the isotropic EXAFS spectra for the S 2 and S 3 structures of the oxygen evolving complex in photosystem II

“…This method is a combination of QM geometry optimization and an EXAFS structure refinement, and is the same used in previous studies (22)(23)(24). Technical details are provided in SI Appendix.…”

“…Therefore, an EXAFS spectrum calculated directly on a DFT structure will be poor, and a direct comparison of DFT and EXAFS distances will also show extensive deviations. Instead, it is better to perform a combined EXAFS/DFT refinement of the EXAFS spectrum, in which the EXAFS raw data (not only the EXAFS distances) are used as a restraint in the DFT geometry optimization (22)(23)(24). Thereby, DFT will determine the general structure of the complex, whereas the EXAFS data will determine the detailed distances involving the metals.…”

Theoretical studies of the active-site structure, spectroscopic and thermodynamic properties, and reaction mechanism of multicopper oxidases

“…full multiple-scattering information), not only a number of bond lengths. It has been employed to interpret the structure of sitting-atop complexes in the metallation of porphyrins and for the oxygen-evolving complex in photosystem II [71,72].…”