55Mn ESE-ENDOR of a Mixed Valence Mn(III)Mn(IV) Complex: Comparison with the Mn Cluster of the Photosynthetic Oxygen-Evolving Complex

Randall, David; Sturgeon, Bradley E.; Ball, James A.; Lorigan, Gary A.; Chan, Michael K.; Klein, Melvin P.; Armstrong, William H.; Britt, R. David

doi:10.1021/ja00152a021

Cited by 115 publications

(168 citation statements)

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“…Based on the magnitude of the hyperfine coupling constants and energy of the transition, it was concluded that the OEC contained a mixed valence manganese cluster [112]. Subsequent analysis suggested that to simulate the OEC spectrum, one needed a cluster of at least three and then four manganese ions to match the EPR, ESEEM and ENDOR spectra [113][114][115]. Thus, this and related Mn III Mn IV species played a crucial role in our early understanding of the enzyme.…”

Section: Mn-μ-o 2 -Mnmentioning

confidence: 99%

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Mullins

Pecoraro

2008

Coordination Chemistry Reviews

327

252

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Recent advances in the study of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) include structural information attained from several X-ray crystallographic (XRD) and spectroscopic (XANES and EXAFS) investigations. The possible structural features gleaned from these studies have enabled synthetic chemists to design more accurate model complexes, which in turn, offer better insight into the possible pathways used by PSII to drive photosynthetic water oxidation catalysis. Mononuclear model compounds have been used to advance the knowledge base regarding the physical properties and reactivity of high-valent (Mn(IV) or Mn(V)) complexes. Such investigations have been especially important in regard to the manganyl (Mn(IV)=O or Mn(V)≡O) species, as there are no reports, to date, of any structural characterized multinuclear model compounds that incorporate such a functionality. Dinuclear and trinuclear model compounds have also been thoroughly studied in attempts to draw further comparison to the physical properties observed in the natural system and to design systems of catalytic relevance. As the reactive center of the OEC has been shown to contain an oxo-Mn(4)Ca cluster, exact structural models necessitate a tetranuclear Mn core. The number of models that make use of Mn(4) clusters has risen substantially in recent years, and these models have provided evidence to support and refute certain mechanistic proposals. Further work is needed to adequately address the rationale for Ca (and Cl) in the OEC and to determine the sequence of events that lead to O(2) evolution.

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Section: Mn-μ-o 2 -Mnmentioning

confidence: 99%

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Mullins

Pecoraro

2008

Coordination Chemistry Reviews

327

252

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“…However, it is generally agreed that deprotonation at the higher S states is more likely, and mechanisms based on deprotonation or H atom abstraction of the substrate, OH − or H 2 O, linked to the tyrosine Z moiety have been proposed. 62,74,75 Alternatively, it has been proposed that formation of peroxide might follow protonation of a bridging μ-oxo ligand in the S 3 state and subsequent release of a dioxygen molecule. 76,77 Whether a peroxo-bridged Mn structure forms in the S 3 state is still under debate.…”

Section: Implication To the Mechanism Of Water Oxidationmentioning

confidence: 99%

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

et al. 2000

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The oxygen-evolving complex of Photosystem II in plants and cyanobacteria catalyzes the oxidation of two water molecules to one molecule of dioxygen. A tetranuclear Mn complex is believed to cycle through five intermediate states (S 0 -S 4 ) to couple the four-electron oxidation of water with the one-electron photochemistry occurring at the Photosystem II reaction center. We have used X-ray absorption spectroscopy to study the local structure of the Mn complex and have proposed a model for it, based on studies of the Mn K-edges and the extended X-ray absorption fine structure of the S 1 and S 2 states. The proposed model consists of two di-μ-oxo-bridged binuclear Mn units with Mn-Mn distances of ~2.7 Å that are linked to each other by a mono-μ-oxo bridge with a Mn-Mn separation of ~3.3 Å. The Mn-Mn distances are invariant in the native S 1 and S 2 states. This report describes the application of X-ray absorption spectroscopy to S 3 samples created under physiological conditions with saturating flash illumination. Significant changes are observed in the Mn-Mn distances in the S 3 state compared to the S 1 and the S 2 states. The two 2.7 Å Mn-Mn distances that characterize the di-μ-oxo centers in the S 1 and S 2 states are lengthened to ~2.8 and 3.0 Å in the S 3 state, respectively. The 3.3 Å Mn-Mn and Mn-Ca distances also increase by 0.04-0.2 Å. These changes in Mn-Mn distances are interpreted as consequences of the onset of substrate/water oxidation in the S 3 state. Mn-centered oxidation is evident during the S 0 →S 1 and S 1 →S 2 transitions. We propose that the changes in Mn-Mn distances during the S 2 →S 3 transition are the result of ligand or water oxidation, leading to the Supporting Information Available: E-space S 3 state EXAFS spectrum; the data in k-space and the background that was removed to reduce the low-frequency contributions that show up as peaks at <1 Å in the Fourier transform; and the Fourier isolate of the k-space S 3 spectrum, shown overplotted on the S 3 EXAFS spectrum (PDF). This material is available free of charge via the Internet at http:// pubs.acs.org. NIH Public Access

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“…Several tetranuclear mixed valence manganese complexes have been prepared as potential models for the OEC of PSII [4][5][6][7][8][9][10][11][12][13][14][15]. To date, the lowest mixed valence tetranuclear clusters that have been reported have average oxidation state 2.5+/Mn and (II,III,II,III) or (II,II,II,IV) moiety [5,7] or with a (l 4 -O)Mn bridging moiety, respectively [8].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, structure and interactions with DNA of novel tetranuclear, [Mn4(II/II/II/IV)] mixed valence complexes

Dimitrakopoulou

Dendrinou‐Samara

Pantazaki

et al. 2008

Journal of Inorganic Biochemistry

231

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55Mn ESE-ENDOR of a Mixed Valence Mn(III)Mn(IV) Complex: Comparison with the Mn Cluster of the Photosynthetic Oxygen-Evolving Complex

Cited by 115 publications

References 1 publication

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Synthesis, structure and interactions with DNA of novel tetranuclear, [Mn4(II/II/II/IV)] mixed valence complexes

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55Mn ESE-ENDOR of a Mixed Valence Mn(III)Mn(IV) Complex: Comparison with the Mn Cluster of the Photosynthetic Oxygen-Evolving Complex

Cited by 115 publications

References 1 publication

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Reflections on small molecule manganese models that seek to mimic photosynthetic water oxidation chemistry

Structural Change of the Mn Cluster during the S2→S3 State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy

Synthesis, structure and interactions with DNA of novel tetranuclear, [Mn4(II/II/II/IV)] mixed valence complexes

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Structural Change of the Mn Cluster during the S₂→S₃ State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy