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Haumann, Michael; Bögershausen, Oliver; Cherepanov, Dmitry A.; Ahlbrink, Ralf; Junge, Wolfgang

doi:10.1023/a:1005861917596

Cited by 116 publications

(133 citation statements)

References 65 publications

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“…Junge and co-workers have proposed a mechanism in which Mn is oxidized during the S 0 →S 1 and S 1 →S 2 transitions but involves the oxidation of bound substrate, OH − , to a hydroxide radical during the S 2 →S 3 transition, with a small fraction already present as a peroxide intermediate. 85,86 The presence of an unpaired electron on the oxygen changes the spin state of the Mn complex; therefore, the MLS signal disappears, as observed from the results of EPR spectroscopy. Parallel-mode EPR studies by Matsukawa and co-workers have shown the presence of EPR resonances at g = 12 and 8 that are best simulated by an S = 1 excited-state spin species in the S 3 state.…”

Section: Implication To the Mechanism Of Water Oxidationmentioning

confidence: 78%

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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Section: Implication To the Mechanism Of Water Oxidationmentioning

confidence: 78%

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 rate of electron transfer during the 02-evolving step S4 -»So was resolved by recording the decay of the absorption transient at 360 nm on flash number three in a series given to dark-adapted material (data here not shown; for examples of raw transients see [24,25]). …”

Section: Rate Of Electron Transfermentioning

confidence: 99%

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol

et al. 1997

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During the four-stepped catalytic cycle of water oxidation by photosystem II (PSII) molecular oxygen is released in only one of the four reaction steps whereas the release of four protons is distributed over all steps. In principle, the pattern of proton production could be taken as indicative of the partial reactions with bound water. In thylakoids the extent and rate of proton release varies as function of the redox transition and of the pH without concomitant variations of the redox pattern. The variation has allowed to discriminate between deprotonation events of peripheral amino acids (Bohr effects) as opposed to the chemical deprotonation of a particular redox cofactor, and of water. In contrast, in thylakoids grown under intermittent light, as well as in PSII core particles the pattern of proton release is flat and independent of the pH. This has been attributed to the lack in these materials of the chlorophyll a,d-binding (CAB) proteins. We now found that a thylakoid-like, oscillatory pattern of proton release was restored simply by the addition of glycerol which modifies the protein-protein interaction. Being a further proof for the electrostatic origin of the greater portion of proton release, this effect will serve as an important tool in further studies of water oxidation.

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“…2A), which describes the sequential accumulation of 4 oxidizing eq (by the manganese complex) before O 2 formation (20). It was found that the rate constants of electron transfer (ET) are only moderately pH-dependent (21,22), so suppres-* This work was supported in part by the Deutsche Forschungsgemeinschaft (SFB 498, Berlin), the UniCat Cluster of Excellence (Unifying Concepts in Catalysis, Berlin), the German Ministry of Education and Research (Bio-H 2 , 03SF0318C; and H 2 Design Cell, 03SF0355D), and the European Union (SOLAR-H2 516510). □ S The on-line version of this article (available at http://www.jbc.org) contains supplemental "Materials and Methods," Figs.…”

mentioning

confidence: 99%

Thermodynamic Limitations of Photosynthetic Water Oxidation at High Proton Concentrations

Zaharieva¹,

Wichmann

Dau

2011

Journal of Biological Chemistry

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In oxygenic photosynthesis, solar energy drives the oxidation of water catalyzed by a Mn 4 Ca complex bound to the proteins of Photosystem II. Four protons are released during one turnover of the water oxidation cycle (S-state cycle), implying thermodynamic limitations at low pH. For proton concentrations ranging from 1 nM (pH 9) to 1 mM (pH 3), we have characterized the low-pH limitations using a new experimental approach: a specific pH-jump protocol combined with time-resolved measurement of the delayed chlorophyll fluorescence after nanosecond flash excitation. Effective pK values were determined for low-pH inhibition of the light-induced S-state transitions: pK 1 ‫؍‬ 3.3 ؎ 0.3, pK 2 ‫؍‬ 3.5 ؎ 0.2, and pK 3 ≈ pK 4 ‫؍‬ 4.6 ؎ 0.2. Alkaline inhibition was not observed. An extension of the classical Kok model facilitated assignment of these four pK values to specific deprotonation steps in the reaction cycle. Our results provide important support to the extended S-state cycle model and criteria needed for assessment of quantum chemical calculations of the mechanism of water oxidation. They also imply that, in intact organisms, the pH in the lumen compartment can hardly drop below 5, thereby limiting the ⌬pH contribution to the driving force of ATP synthesis.Light-driven water oxidation by plants, algae, and cyanobacteria is a pivotal process in biological solar energy conversion (1). Its evolutionary development, ϳ3.5 billion years ago, has boosted life on Earth by facilitating the efficient use of water as a source of electrons and protons for the synthesis of energystoring carbohydrates and biomass in general. The long-standing scientific interest in photosynthetic water oxidation has recently been invigorated by the vision of future technological systems that, akin to plants and cyanobacteria, use water as a substrate for light-driven formation of energy-rich and storable compounds (H 2 or other fuel materials) (2-5). We believe that insights into energetics and reaction mechanisms of the natural paragon could provide inspiration and guidelines for the development of new technologies (6 -8). However, the biological process is understood only insufficiently (9).In oxygenic photosynthesis, solar energy drives the oxidation of water and the accumulation of "energized" electrons by reduction of quinones (Fig.

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Cited by 116 publications

References 65 publications

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

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

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol

Thermodynamic Limitations of Photosynthetic Water Oxidation at High Proton Concentrations

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Untitled

Cited by 116 publications

References 65 publications

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

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

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol

Thermodynamic Limitations of Photosynthetic Water Oxidation at High Proton Concentrations

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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

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