Water‐Splitting Chemistry of Photosystem II

McEvoy, James P.; Brudvig, Gary W.

doi:10.1002/chin.200702228

Cited by 205 publications

(351 citation statements)

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“…The OEC is electrically linked to P680 by a redox-active tyrosine residue. The oxidized form of tyrosine reside is the radical species, which exists in the neutral deprotonated form [43,44]. A recent paper revealing the redox features of PSII in protein-film voltammetric mode [45] describes quite similar features of PSII-OEC system to those described in this theoretical work.…”

Section: Discussionmentioning

confidence: 63%

“…All mentioned theoretical features of considered protein-film EEC′ mechanism in this work can be of big practical relevance for studying the redox features of many proteins containing quinone moiety or polyvalent ions of transitions metals as Mo, Mn, W, or Co as redox centers [26]. A relevant biological example of the elaborated EEC′ mechanism is found by the processes of water oxidation to oxygen (O 2 ) by the Photosystem II (PSII or P680) [43,44]. It is well-known that the dioxygen molecules are derived from water that is oxidized to O 2 by the PSII enzyme.…”

Section: Discussionmentioning

confidence: 99%

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Catalytic mechanism in successive two-step protein-film voltammetry—Theoretical study in square-wave voltammetry

Gulaboski

Mihajlov

2011

Biophysical Chemistry

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Protein-film voltammetry is established as an effective tool that provides insight to the redox features of various lipophilic proteins by using a simple methodology. Although the protein-film experimental set up is relatively simple, the redox mechanisms of many proteins are quite complicated, and very often they cannot be resolved without having support from adequate mathematical models. In this work we continue our contribution to modeling relevant redox mechanisms in protein-film voltammetry. We present results from the theoretical simulations of catalytic mechanism at the two-step successive surface redox reaction under conditions of square-wave voltammetry. This mechanism is assigned as a surface EEC′, and it can be presented by the following simplified scheme: A(ads) + ne− ⇄ B(ads) + ne− ⇄ C(ads) + Substrate → kcat B(ads). Our attention is focused on several phenomena of this complex protein-film mechanism, while we give set of qualitative criteria to distinguish this mechanism from similar ones studied under voltammetric conditions. Moreover, we also provide hints to use methodologies for the determination of thermodynamic and kinetic parameters relevant to the protein-film EEC′ mechanism. The considered protein-film EEC′ mechanism is applicable to all lipophilic redox proteins that undergo electrochemical transformations in more than one successive electron steps. Such examples exist by proteins containing quinone moiety and some polyvalent ions of transition metals as redox active sites.

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Catalytic mechanism in successive two-step protein-film voltammetry—Theoretical study in square-wave voltammetry

Gulaboski

Mihajlov

2011

Biophysical Chemistry

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“…The direct photoelectrochemical (PEC) conversion of solar energy into storable fuels, which is based on cheap and earth-abundant semiconductors and catalysts, has the potential to satisfy these requirements. [1][2][3][4][5][6] Metal-oxide semiconductors are particularly appealing candidates for practical applications because of their low cost, nontoxicity, abundance, and stability toward corrosion.…”

Section: Introductionmentioning

confidence: 99%

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

et al. 2016

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We discuss here for the first time how to combine iron and titanium metal ions to achieve a high photo-electrochemical activity for TiO 2 -based photo-anodes in water splitting devices. To do so, a wide range of photoelectrode materials with tailored Ti/Fe ratio and element vicinity were synthesized by using the versatility of aqueous sol-gel chemistry in combination with a microwave-assisted crystallization process. At low ferric concentrations, single phase TiO 2 anatase doped with various Fe amounts were prepared. Strikingly, at higher ferric concentrations, propose that the nature of the heterojunction impacts charge carrier recombination. The results presented herein not only answer whether iron and titanium should be combined in the same structure or into heterostructured systems, but also on the importance of the arrangement of ions in the structure to improve the performances of the photoanode.

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“…PS II appears to catalyze water oxidation at a pentanuclear Mn 4 Ca cluster that accumulates oxidizing equivalents (see recent reviews in refs. [1][2][3][4][5]. It is generally supposed that the water oxidation is triggered by charge separation between the primary electron donor, P680, and the primary electron acceptor, pheophytin (Phe) a.…”

mentioning

confidence: 99%

“…It is generally supposed that the water oxidation is triggered by charge separation between the primary electron donor, P680, and the primary electron acceptor, pheophytin (Phe) a. The initial radical pair P680 ϩ Phe a Ϫ formed by the charge separation, drives forward electron transfer from Phe a Ϫ to the first plastoquinone Q A , and hole transfer from P680 ϩ to the Mn 4 Ca cluster through a redox-active tyrosine residue denoted Y Z , thus preventing charge recombination. Recent X-ray crystallography clarified the arrangement of protein subunits and cofactors in PS II with 2.9-3.7-Å resolution (6)(7)(8)(9), visualizing the electron transfer pathway.…”

mentioning

confidence: 99%

Spectroelectrochemical determination of the redox potential of pheophytina, the primary electron acceptor in photosystem II

Kato

Sugiura

Oda

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Thin-layer cell spectroelectrochemistry, featuring rigorous potential control and rapid redox equilibration within the cell, was used to measure the redox potential Em(Phe a/Phe a ؊ ) of pheophytin (Phe) a, the primary electron acceptor in an oxygen-evolving photosystem (PS) II core complex from a thermophilic cyanobacterium Thermosynechococcus elongatus. Interferences from dissolved O 2 and water reductions were minimized by airtight sealing of the sample cell added with dithionite and mercury plating on the gold minigrid working electrode surface, respectively. The result obtained at a physiological pH of 6.5 was E m(Phe a/Phe a ؊ ) ‫؍‬ ؊505 ؎ 6 mV vs. SHE, which is by Ϸ100 mV more positive than the values measured Ϸ30 years ago at nonphysiological pH and widely accepted thereafter in the field of photosynthesis research. Using the P680* ؊ Phe a free energy difference, as estimated from kinetic analyses by previous authors, the present result would locate the E m(P680/P680 ؉ ) value, which is one of the key parameters but still resists direct measurements, at approximately ؉1,210 mV. In view of these pieces of information, a renewed diagram is proposed for the energetics in PS II.charge separation ͉ photosynthesis ͉ spectroelectrochemistry ͉ water oxidation I n the photosynthetic primary process of higher plants, algae, and cyanobacteria, photosystem (PS) I and PS II cooperate in series to convert photon energy into chemical energy through light-induced charge separation and subsequent electron transfers. PS II appears to catalyze water oxidation at a pentanuclear Mn 4 Ca cluster that accumulates oxidizing equivalents (see recent reviews in refs. 1-5). It is generally supposed that the water oxidation is triggered by charge separation between the primary electron donor, P680, and the primary electron acceptor, pheophytin (Phe) a. The initial radical pair P680 ϩ Phe a Ϫ formed by the charge separation, drives forward electron transfer from Phe a Ϫ to the first plastoquinone Q A , and hole transfer from P680 ϩ to the Mn 4 Ca cluster through a redox-active tyrosine residue denoted Y Z , thus preventing charge recombination. Recent X-ray crystallography clarified the arrangement of protein subunits and cofactors in PS II with 2.9-3.7-Å resolution (6-9), visualizing the electron transfer pathway.To date, the nature of P680 remains controversial. Available experimental data and theoretical analyses suggest that P680 is assignable to the pigment cluster of the four chlorophyll a molecules (denoted P D1 , P D2 , Chl D1 , and Chl D2 ) in the PS II reaction center (1, 5). Further uncertainty surrounds the value of the redox potential E m (P680/P680 ϩ ). Although the E m (P680/ P680 ϩ ) value is an essential parameter to draw a whole picture of the PS II energetics, its direct measurement has never been attained (10) because water, present as dominant (solvent) molecules in most sample solutions, is oxidized first heavily and tends to mask the subsequent oxidation of the target entity P680 at a higher potential. The E m ...

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Water‐Splitting Chemistry of Photosystem II

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Cited by 205 publications

References 1 publication

Catalytic mechanism in successive two-step protein-film voltammetry—Theoretical study in square-wave voltammetry

Catalytic mechanism in successive two-step protein-film voltammetry—Theoretical study in square-wave voltammetry

How Should Iron and Titanium be Combined in Oxides to Improve Photoelectrochemical Properties?

Spectroelectrochemical determination of the redox potential of pheophytina, the primary electron acceptor in photosystem II

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