Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

Klein, Melvin P.; Sauer, Kenneth; Yachandra, Vittal K.

doi:10.1007/bf00046751

Cited by 61 publications

(48 citation statements)

References 58 publications

(66 reference statements)

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“…These flash patterns are explained by the proposed oxidation states of the Mn cluster in the S 0 , S 1 , S 2 , and S 3 states, as shown in Figure 10. Consistent with earlier proposals, 8,49,132 …”

Section: Effects Of Structural Changes On the Xanes And Kβ Xes Datasupporting

confidence: 89%

Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

et al. 2001

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A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen-evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S 3 → [S 4 ] → S 0 transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn Kβ X-ray emission spectroscopy (Kβ XES) to this problem for the first time. The Kβ XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S 2 → S 3 transition, in contrast to the S 0 → S 1 and S 1 → S 2 transitions, does not involve a Mn-centered oxidation. On the basis of new structural data from the S 3 -state, manganese μ-oxo bridge radical formation is proposed for the S 2 → S 3 transition, and three possible mechanisms for the O-O bond formation are presented.

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Section: Effects Of Structural Changes On the Xanes And Kβ Xes Datasupporting

confidence: 89%

Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

et al. 2001

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“…9), indicating three successive oxidation steps of Mn up to S3. A shift coupled with the S2+S3 transition was, however, not observed by Klein et al [61]. It was assumed that an amino acid residue (histidine?)…”

Section: Mn Oxidationmentioning

confidence: 82%

“…Strong support for the conclusion that these S-state transitions are due to oxidations of Mn has been obtained from X-ray absorption spectroscopy. With this method the position of the K-edge of Mn was measured by Klein et al as a function of the S-state transitions [61]. Three distinct K-edge shifts of ca.…”

Section: Mn Oxidationmentioning

confidence: 99%

Primary reactions of oxygenic photosynthesis

Witt

1996

Ber Bunsenges Phys Chem

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“…The oxygen evolving complex (OEC) has been recently reviewed by , , Klein et al (1993); Pistorius (1993), Renger (1993); and Sauer et al (1992). Oxidation of water by the OEC does not occur in a single step.…”

Section: The Oxygen Evolving Complex: Spectroscopic Methods and Currementioning

confidence: 99%

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

Andrews

1995

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In this study, oriented Photosystem 11 (PS n) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy VAS) to determine more details of the structure of the oxygen evolving complex (OEC).The nature of halide binding to Mn is also studied with C1 K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-C1 model compounds, and with Mn EXAFS of oriented PS 1T in which Br has replaced C1.In chapter 2, oriented PS 11 particles from spinach were studied with EPR spectroscopy. The mosaic spread for these samples was determined by comparison of the oxidized cytochrome b559 (cyt b559+) signal measured at angles of 0" to 360" between the EPR magnetic field and sample membrane normal with simulations of oriented cyt b559+.The tyrosine YD+ signal was measured for these oriented samples at 0" and 90°, and a linear relationship was found between the dichroism found in the tyrosine YD+ signal and the mosaic spread.In chapters 3 and 4, Mn XAS was performed on oriented PS 11 membrane particles isolated from spinach. These studies were on control samples (chapter 3) and on samples treated with ammonia (chapter 4), a water analog which can yield insight into the binding of water by the OEC. Structural features of the tetranuclear Mn cluster and the orientation of the cluster with respect to the lipid bilayer were determined in the S2 state of the Kok cycle 1 for control samples, and on the annealed S2 state for the ammonia-treated samples.Variation of the sample orientation with respect to the x-ray e-vector yields highly dichroic In chapter 5, the binding of halide to Mn was studied using C1 K-edge XAS and Mn EXAFS on Mn-CI model compounds, and Mn EXAFS on oriented Br-treated PS IL From the C1 K-edges of model compounds, direct ligation of C1 to Mn could be confirmed with the presence of a pre-edge feature: 'a forbidden 1s to 3d transition which is seen due to mixing of Mn 3d orbitals with C13p orbitals. Bridging and terminal C1 bonds to Mn could be distinguish& EXAFS of Mn-C1 model compounds revealed that Mn-C1 interactions, especially bridging interactions, make an important contribution to the EXAFS. EXAFS of oriented Br-treated PS 11 showed differences from EXAFS of control CI-treated PS II that were on the same order as the variation from sample to sample. Fits to Br-treated and Cl control samples were also inconclusive. Thus, it is not possible to 9 establish or rule out direct ligation of C1 to Mn in the OEC with these studies.2

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Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

Cited by 61 publications

References 58 publications

Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

Primary reactions of oxygenic photosynthesis

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

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Perspectives on the structure of the photosynthetic oxygen evolving manganese complex and its relation to the Kok cycle

Cited by 61 publications

References 58 publications

Absence of Mn-Centered Oxidation in the S2→ S3Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

Absence of Mn-Centered Oxidation in the S2→ S3Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

Primary reactions of oxygenic photosynthesis

X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

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Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation

Absence of Mn-Centered Oxidation in the S₂→ S₃Transition: Implications for the Mechanism of Photosynthetic Water Oxidation