Structural characterization of the manganese sites in the photosynthetic oxygen-evolving complex using x-ray absorption spectroscopy

Penner‐Hahn, James E.; Fronko, Richard M.; Pecoraro, Vincent L.; Yocum, Charles F.; Betts, Scott D.; Bowlby, Neil R.

doi:10.1021/ja00163a011

Cited by 188 publications

(199 citation statements)

References 20 publications

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“…With this in mind, we would like to note that previous EXAFS characterization of the Mn 4 Ca cluster of the OEC at each S-state [14][15][16][17] show that the structural changes observed after each oxidizing step are comparable to those measured in these model compounds (MnMn distance changes of 0.1-0.3 Å). The reported XANES K-edge energy shift for S 0 → S 1 (proposed Mn II→III oxidation) [16][17][18] is also comparable in magnitude to those observed in this study, while the K-edge energy shifts for the S 1 → S 2 and S 2 → S 3 transitions are smaller. Evidently both Mn oxidation and ligand interactions have an effect on the observed XAS.…”

Section: Discussionsupporting

confidence: 85%

“…[14][15][16][17] Previous XAS studies show that there is a consensus of Mn-Mn interactions within the cluster with one mono-μ-oxo (~3.3 Å) and two or three di-μ-oxo (~2.7 Å) bridges. [16][17][18] Sr and Ca EXAFS have demonstrated the proximity of Ca(Sr) to the Mn and the presence of a Mn 4 Ca cluster in the OEC. 19,20 The ultimate structure of the OEC has significant implications for the mechanism of water oxidation.…”

Section: Introductionmentioning

confidence: 99%

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Mn oxidation states in tri- and tetra-nuclear Mn compounds structurally relevant to photosystem II: Mn K-edge X-ray absorption and K? X-ray emission spectroscopy studies

Pizarro

Glatzel

Visser

et al. 2004

Phys. Chem. Chem. Phys.

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X-Ray spectroscopy is used to examine the effect of the manganese oxidation state for a series of Mn model compounds. Sensitive to Mn oxidation and structural symmetry, X-ray absorption and emission spectroscopy (XAS and XES) provide complementary insights. However, few benchmark examples of complexes with similar structures but in different oxidation states are available to evaluate data from unknown structures like the oxygen evolving complex (OEC) of Photosystem II (PSII). This study examines two types of compounds prepared in a variety of Mn oxidation states and which possess chemical structures with Mn-Mn interactions (~2.7 Å and ~3.3 Å) that have been observed in the OEC. Model complexes with core compositions Mn 3 O and Mn 4 O 2 contain combinations of Mn in either a reduced (II) or oxidized (III) state. Within each set of compounds, complexes with higher Mn oxidation states have absorption K-edge energy values that are higher (1.6-2.2 eV) than those of their more reduced counterparts. This trend is accordingly reversed in the Kβ emission spectroscopy where the first moment energy values are lower (0.09-0.12 eV) for compounds with higher Mn oxidation states. We will discuss in detail, how these trends can be quantitatively used to characterize the effects of the Mn oxidation state as well as the surrounding ligand environment on the observed X-ray spectra. The results are discussed with respect to previously obtained data on different S-states of the OEC.

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Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Mn oxidation states in tri- and tetra-nuclear Mn compounds structurally relevant to photosystem II: Mn K-edge X-ray absorption and K? X-ray emission spectroscopy studies

Pizarro

Glatzel

Visser

et al. 2004

Phys. Chem. Chem. Phys.

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“…This technique has been shown to be reasonably accurate for the determination of Mn(II). 32,59 The shape of the edge of the S 2 ′-annealed sample in the region of the inflection point was, however, not well-simulated using the hexaquo Mn(II) spectrum.…”

Section: X-ray Edge Spectroscopymentioning

confidence: 99%

Structural Effects of Calcium Depletion on the Manganese Cluster of Photosystem II: Determination by X-ray Absorption Spectroscopy

et al. 1998

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The structural consequences of calcium depletion of Photosystem II (PS II) by treatment at pH 3.0 in the presence of citrate has been determined by Mn K-edge X-ray absorption spectroscopy. Xray absorption edge spectroscopy of Ca-depleted samples in the S 1 ′, S 2 ′, and S 3 ′ oxidation states reveals that there is Mn oxidation on the S 1 ′-S 2 ′ transition, although no evidence of Mn oxidation was found for the S 2 ′-S 3 ′ transition. This result is in keeping with the results from EPR studies where it has been found that the species oxidized to give the S 3 ′ broad radical signal found in Cadepleted PS II is tyrosine Y z . The S 2 ′ state can be prepared by two methods: illumination followed by dark adaptation and illumination in the presence of DCMU to limit to one turnover. Illumination followed by dark adaptation was found to yield a lower Mn K-edge inflection-point energy than illumination with DCMU, indicating vulnerability to reduction of the Mn complex, even over the relatively short times used for dark adaptation (~15 min). EXAFS measurements of Ca-depleted samples in the three modified S states (referred to here as S′ states) reveals that the Fourier peak due to scatterers at ~3.3 Å from Mn is strongly diminished, consistent with our previous assignment of a Ca-scattering contribution at this distance. Even after Ca depletion, there is still significant amplitude in the third peak, further supporting our conclusions from earlier studies that the third peak in native samples is comprised of both Mn and Ca scattering. The MnMn contributions making up the second Fourier peak at ~2.7 Å are largely undisturbed by Cadepletion, but there is some evidence that S 1 ′-state samples contain significant amounts of reduced Mn(II), which is then photooxidized in the preparation of higher S′ states.

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“…These conclusions were obtained after a careful comparison of the second derivative analyses of the XAS edge and pre-edge features of many Mn model compounds . These assignments are now generally agreed upon by the XAS-OEC community (Kusunoki et al, 1990;Penner-Hahn et al, 1992).…”

Section: Ib32 the Results From Xasmentioning

confidence: 81%

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

Liang¹

1994

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Structural characterization of the manganese sites in the photosynthetic oxygen-evolving complex using x-ray absorption spectroscopy

Cited by 188 publications

References 20 publications

Mn oxidation states in tri- and tetra-nuclear Mn compounds structurally relevant to photosystem II: Mn K-edge X-ray absorption and K? X-ray emission spectroscopy studies

Mn oxidation states in tri- and tetra-nuclear Mn compounds structurally relevant to photosystem II: Mn K-edge X-ray absorption and K? X-ray emission spectroscopy studies

Structural Effects of Calcium Depletion on the Manganese Cluster of Photosystem II: Determination by X-ray Absorption Spectroscopy

Structural oxidation state studies of the manganese cluster in the oxygen evolving complex of photosystem II

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