The Possible Role of Proton‐Coupled Electron Transfer (PCET) in Water Oxidation by Photosystem II

Meyer, Thomas J.; Huynh, My Hang V.; Thorp, H. Holden

doi:10.1002/anie.200600917

Cited by 512 publications

(403 citation statements)

References 237 publications

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“…In these proposals 32,33,98 it is assumed that the known structural changes during the S 2 / S 3 transition lead to a situation that in a small fraction of PSII complexes (about 10-15%) a formation of the O-O bond in form of a complexed peroxide occurs already in the S 3 state. This state is assumed to exist within an redox equilibrium of various other forms of S 3 that may include an oxygen radical and/or a Mn 4 (IV,IV,IV,IV) state.…”

Section: 9697mentioning

confidence: 99%

Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases

Lubitz¹,

Reijerse²,

Messinger³

2008

Energy Environ. Sci.

402

362

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This review aims at presenting the principles of water-oxidation in photosystem II and of hydrogen production by the two major classes of hydrogenases in order to facilitate application for the design of artificial catalysts for solar fuel production. W: Lubitz E: Reijerse J: Messinger W. Lubitz is director of the MPI for Bioinorganic Chemistry and a specialist in advanced EPR techniques. He has a strong interest in both water-splitting and hydrogen production. E. Reijerse is working on hydrogenases using FTIR and EPR/ENDOR spectroscopies. J. Messinger is analyzing photosynthetic and artificial water-splitting employing O 2 measurements, mass spectrometry (MIMS), EPR and XAS.

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Section: 9697mentioning

confidence: 99%

Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases

Lubitz¹,

Reijerse²,

Messinger³

2008

Energy Environ. Sci.

402

362

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“…In chelating action of polyphenols, the proton loss is crucial for the protective activity of these natural antioxidants, too (Procházková et al 2011). In general, proton transfer represents an important step in many processes in biological systems or processes of organic syntheses (Meyer et al 2007). For complex study of reaction mechanisms in solution-phase, the knowledge of proton solvation enthalpies in various non-polar and polar solvents is essential.…”

Section: Introductionmentioning

confidence: 99%

Solvation enthalpies of the proton in polar and non-polar solvents: Theoretical study

Rottmannová¹,

Škorňa²,

Rimarčík³

et al. 2013

Acta Chimica Slovaca

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In spite of the importance of proton transfer in solution-phase processes, there is still no systematic theoretical study of proton solvation enthalpies. We have investigated the solvation enthalpies of the proton in seven solvents of various polarities (benzene, chloroform, acetone, methanol, ethanol, DMSO, water) using the Integral Equation Formalism Polarized Continuum Model (IEF-PCM). All computations were performed at the B3LYP and BHLYP levels of theory with aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ basis sets. Our calculations have shown that the B3LYP and BHLYP functionals provide similar solvation enthalpies. Finally, differences in the solvation enthalpy of the proton values stemming from the various basis sets do not exceed 6 kJ mol -1 , with exception of DMSO and chloroform. Distance between H + and the acceptor atom of the solvent molecule is the shortest in the case of water. It has been also found that the B3LYP distances are slightly longer.

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“…Tyr Z OH is oxidized by long-range electron transfer to a photoexcited chlorophyll (P 680 ϩ ), with the proton likely transferred to the imidazole moiety of a nearby histidine (H 190 ) (6). Tyr Z O…”

mentioning

confidence: 99%

“…These processes likely proceed by separated CPET, with the e Ϫ and H ϩ transferring in a single kinetic step involving multiple sites (6).…”

mentioning

confidence: 99%

Probing concerted proton–electron transfer in phenol–imidazoles

Markle

Rhile

DiPasquale

et al. 2008

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

122

188

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A series of seven substituted 4,6-di-tert-butyl-2-(4,5-diarylimidazolyl)-phenols have been prepared and characterized, along with two related benzimidazole compounds. X-ray crystal structures of all of the compounds show that the phenol and imidazole rings are close to coplanar and are connected by an intramolecular ArOH⅐ ⅐ ⅐N hydrogen bond. One-electron oxidation of these compounds occurs with movement of the phenolic proton to the imidazole base by concerted proton-electron transfer (CPET) to yield fairly stable distonic radical cations. These phenol-base compounds are a valuable system in which to examine the key features of CPET. Kinetic measurements of bimolecular CPET oxidations, with E rxn between ؉0.04 and ؊0.33 V, give rate constants from (6.3 ؎ 0.6) ؋ 10 2 to (3.0 ؎ 0.6) ؋ 10 6 M ؊1 s ؊1 . There is a good correlation of log(k) with ⌬G°, with only one of the 15 rate constants falling more than a factor of 5.2 from the correlation line. Substituents on the imidazole affect the (O-H⅐ ⅐ ⅐N) hydrogen bond, as marked by variations in the 1 H NMR and calculated vibrational spectra and geometries. Crystallographic dO⅐ ⅐ ⅐N values appear to be more strongly affected by crystal packing forces. However, there is almost no correlation of rate constants with any of these measured or computed parameters. Over this range of compounds from the same structural family, the dominant contributor to the differences in rate constant is the driving force ⌬G°.Marcus Theory ͉ oxyl radicals ͉ proton-coupled ͉ ROS ͉ tyrosyl radicals R eactive oxygen species (ROS) exhibit a wide range of reactivity, from the extraordinarily potent hydroxyl radical to much more inert aryloxyl and ascorbyl radicals. These species are sometimes categorized by their redox potentials at pH 7, but most reactions of ROS do not proceed by simple electron transfer (ET). Typically, ROS react by proton-coupled electron transfer (PCET), as in the disproportionation of hydrogen peroxide to dioxygen and water and the interconversions of tyrosyl radicals and tyrosine residues. Understanding the detailed mechanisms of these and other PCET

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The Possible Role of Proton‐Coupled Electron Transfer (PCET) in Water Oxidation by Photosystem II

Cited by 512 publications

References 237 publications

Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases

Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases

Solvation enthalpies of the proton in polar and non-polar solvents: Theoretical study

Probing concerted proton–electron transfer in phenol–imidazoles

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