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Demchenko AP. Proton transfer reactions: from photochemistry to biochemistry and bioenergetics. BBA ADVANCES 2023. [DOI: 10.1016/j.bbadva.2023.100085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023] Open
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2
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Gindt YM, Connolly G, Vonder Haar AL, Kikhwa M, Schelvis JPM. Investigation of the pH-dependence of the oxidation of FAD in VcCRY-1, a member of the cryptochrome-DASH family. Photochem Photobiol Sci 2021; 20:831-841. [PMID: 34091863 DOI: 10.1007/s43630-021-00063-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/31/2021] [Indexed: 11/29/2022]
Abstract
Vibrio cholerae cryptochrome-1 (VcCRY-1) is a member of the cryptochrome DASH family. The flavoprotein appears to use blue light both for repair of cyclobutane pyrimidine dimers (CPDs) on DNA and signal transduction. Earlier, we found that it was almost impossible to oxidize the FADH· state upon binding to a CPD, and, in the absence of substrate, the rate of FADH· oxidation was much larger at high pH (Gindt et al. in Biochemistry 54:2802-2805, 2015). Here, we present the pH-dependence of the oxidation of FADH· by ferricyanide, which revealed a switch between slow and fast oxidation with a pKa ≈ 7.0. Stopped-flow mixing was used to measure the oxidation of FADH- to FADH· at pH 6.7 and 7.5. Substrate binding was required to slow down this oxidation such that it could be measured with stopped flow, but there was only a small effect of pH. In addition, resonance Raman measurements of FADH· in VcCRY-1 at pH 6.5 and 7.5 were performed to probe for structural changes near the FAD cofactor related to the observed changes in rate of FADH· oxidation. Only substrate binding seemed to induce a change near the FAD cofactor that may relate to the change in oxidation kinetics. The pH-effect on the FADH· oxidation rate, which is rate-limited by the proton acceptor, does not seem to be due to a protein structural change near the FAD cofactor. Instead, a conserved glutamate in CRY-DASH may control the deprotonation of FADH· and give rise to the pH-effect.
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Affiliation(s)
- Yvonne M Gindt
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Gabrielle Connolly
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Amy L Vonder Haar
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Miryam Kikhwa
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA
| | - Johannes P M Schelvis
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, 07043, USA.
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3
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Einholz C, Nohr D, Rodriguez R, Topitsch A, Kern M, Goldmann J, Chileshe E, Okasha M, Weber S, Schleicher E. pH-dependence of signaling-state formation in Drosophila cryptochrome. Arch Biochem Biophys 2021; 700:108787. [PMID: 33545100 DOI: 10.1016/j.abb.2021.108787] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/22/2021] [Accepted: 01/25/2021] [Indexed: 11/30/2022]
Abstract
Cryptochromes, FAD-dependent blue light photoreceptors, undergo a series of electron transfer reactions after light excitation. Time-resolved optical spectroscopy was employed to investigate the pH dependence of all light-dependent reactions in the cryptochrome from fruit flies. Signal state formation experiments on a time scale of seconds were found to be strongly pH dependent, and formation of both anionic and neutral FAD radicals could be detected, with reaction rates increasing by a factor of ~2.5 from basic to neutral pH values. Additionally, the influence of the amino acid His378 was investigated in further detail: Two protein variants, DmCry H378A and H378Q, showed significantly reduced rate constants for signal state formation, which again differed at neutral and alkaline pH values. Hence, His378 was identified as an amino acid responsible for the pronounced pH dependence; however, this amino acid can be excluded as a proton donor for the protonation of the anionic FAD radical. Other conserved amino acids appear to alter the overall polarity of the binding pocket and thus to be responsible for the pronounced pH dependence. Furthermore, the influence of pH and other experimental parameters, such as temperature, glycerol or ferricyanide concentrations, on the intermediately formed FAD-tryptophan radical pair was explored, which deprotonates on a microsecond time scale with a clear pH dependence, and subsequently recombines within milliseconds. Surprisingly, the latter reaction showed no pH dependence; potential reasons are discussed. All results are reviewed in terms of the photoreceptor and potential magnetoreceptor functions of Drosophila cryptochrome.
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Affiliation(s)
- Christopher Einholz
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Daniel Nohr
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Ryan Rodriguez
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Annika Topitsch
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Maria Kern
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Jacqueline Goldmann
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Emma Chileshe
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Moustafa Okasha
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104, Freiburg, Germany.
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4
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Xu Y, Bao P, Song K, Shi Q. Theoretical study of proton coupled electron transfer reaction in the light state of the AppA BLUF photoreceptor. J Comput Chem 2018; 40:1005-1014. [PMID: 30341953 DOI: 10.1002/jcc.25561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/01/2018] [Accepted: 07/24/2018] [Indexed: 11/10/2022]
Abstract
The BLUF (blue light sensor using flavin adenine dinucleotide) domain is widely studied as a prototype for proton coupled electron transfer (PCET) reactions in biological systems. In this work, the photo-induced concerted PCET reaction from the light state of the AppA BLUF domain is investigated. To model the simultaneous transfer of two protons in the reaction, two-dimensional potential energy surfaces for the double proton transfer are first calculated for the locally excited and charge transfer states, which are then used to obtain the vibrational wave function overlaps and the vibrational energy levels. Contributions to the PCET rate constant from each pair of vibronic states are then analyzed using the theory based on the Fermi's golden rule. We show that, the recently proposed light state structure of the BLUF domain with a tautomerized Gln63 residue is consistent with the concerted transfer of one electron and two protons. It is also found that, thermal fluctuations of the protein structure, especially the proton donor-acceptor distances, play an important role in determining the PCET reaction rate. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Yang Xu
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Peng Bao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Kai Song
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qiang Shi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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5
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Glover SD, Parada GA, Markle TF, Ott S, Hammarström L. Isolating the Effects of the Proton Tunneling Distance on Proton-Coupled Electron Transfer in a Series of Homologous Tyrosine-Base Model Compounds. J Am Chem Soc 2017; 139:2090-2101. [DOI: 10.1021/jacs.6b12531] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Starla D. Glover
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Giovanny A. Parada
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Todd F. Markle
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Sascha Ott
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
| | - Leif Hammarström
- Department of Chemistry−Ångström, Uppsala University, Box
532, SE-751 20, Uppsala, Sweden
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6
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Schelvis JPM, Gindt YM. A Review of Spectroscopic and Biophysical-Chemical Studies of the Complex of Cyclobutane Pyrimidine Dimer Photolyase and Cryptochrome DASH with Substrate DNA. Photochem Photobiol 2017; 93:26-36. [PMID: 27891613 DOI: 10.1111/php.12678] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 11/02/2016] [Indexed: 01/02/2023]
Abstract
Cyclobutane pyrimidine dimer (CPD) photolyase (PL) is a structure-specific DNA repair enzyme that uses blue light to repair CPD on DNA. Cryptochrome (CRY) DASH enzymes use blue light for the repair of CPD lesions on single-stranded (ss) DNA, although some may also repair these lesions on double-stranded (ds) DNA. In addition, CRY DASH may be involved in blue light signaling, similar to cryptochromes. The focus of this review is on spectroscopic and biophysical-chemical experiments of the enzyme-substrate complex that have contributed to a more detailed understanding of all the aspects of the CPD repair mechanism of CPD photolyase and CRY DASH. This will be performed in the backdrop of the available X-ray crystal structures of these enzymes bound to a CPD-like lesion. These structures helped to confirm conclusions that were drawn earlier from spectroscopic and biophysical-chemical experiments, and they have a critical function as a framework to design new experiments and to interpret new experimental data. This review will show the important synergy between X-ray crystallography and spectroscopic/biophysical-chemical investigations that is essential to obtain a sufficiently detailed picture of the overall mechanism of CPD photolyases and CRY DASH proteins.
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Affiliation(s)
| | - Yvonne M Gindt
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ
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7
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Miller DC, Tarantino KT, Knowles RR. Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities. Top Curr Chem (Cham) 2016; 374:30. [PMID: 27573270 PMCID: PMC5107260 DOI: 10.1007/s41061-016-0030-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/21/2016] [Indexed: 10/21/2022]
Abstract
Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter, we aim to highlight the origins, development, and evolution of the PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.
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Affiliation(s)
- David C Miller
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Kyle T Tarantino
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Robert R Knowles
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.
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8
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Müller P, Brettel K, Grama L, Nyitrai M, Lukacs A. Photochemistry of Wild-Type and N378D Mutant E. coli DNA Photolyase with Oxidized FAD Cofactor Studied by Transient Absorption Spectroscopy. Chemphyschem 2016; 17:1329-40. [PMID: 26852903 DOI: 10.1002/cphc.201501077] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Indexed: 01/02/2023]
Abstract
DNA photolyases (PLs) and evolutionarily related cryptochrome (CRY) blue-light receptors form a widespread superfamily of flavoproteins involved in DNA photorepair and signaling functions. They share a flavin adenine dinucleotide (FAD) cofactor and an electron-transfer (ET) chain composed typically of three tryptophan residues that connect the flavin to the protein surface. Four redox states of FAD are relevant for the various functions of PLs and CRYs: fully reduced FADH(-) (required for DNA photorepair), fully oxidized FADox (blue-light-absorbing dark state of CRYs), and the two semireduced radical states FAD(.-) and FADH(.) formed in ET reactions. The PL of Escherichia coli (EcPL) has been studied for a long time and is often used as a reference system; however, EcPL containing FADox has so far not been investigated on all relevant timescales. Herein, a detailed transient absorption study of EcPL on timescales from nanoseconds to seconds after excitation of FADox is presented. Wild-type EcPL and its N378D mutant, in which the asparagine facing the N5 of the FAD isoalloxazine is replaced by aspartic acid, known to protonate FAD(.-) (formed by ET from the tryptophan chain) in plant CRYs in about 1.5 μs, are characterized. Surprisingly, the mutant protein does not show this protonation. Instead, FAD(.-) is converted in 3.3 μs into a state with spectral features that are different from both FADH(.) and FAD(.-) . Such a conversion does not occur in wild-type EcPL. The chemical nature and formation mechanism of the atypical FAD radical in N378D mutant EcPL are discussed.
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Affiliation(s)
- Pavel Müller
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
| | - Klaus Brettel
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
| | - Laszlo Grama
- Department of Biophysics, Medical School, University of Pecs, 12 str. Szigeti, 7624, Pecs, Hungary
| | - Miklos Nyitrai
- Department of Biophysics, Medical School, University of Pecs, 12 str. Szigeti, 7624, Pecs, Hungary
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pecs, 12 str. Szigeti, 7624, Pecs, Hungary.
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9
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Gindt YM, Messyasz A, Jumbo PI. Binding of Substrate Locks the Electrochemistry of CRY-DASH into DNA Repair. Biochemistry 2015; 54:2802-5. [PMID: 25910181 DOI: 10.1021/acs.biochem.5b00307] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
VcCry1, a member of the CRY-DASH family, may serve two diverse roles in vivo, including blue-light signaling and repair of UV-damaged DNA. We have discovered that the electrochemistry of the flavin adenine dinucleotide cofactor of VcCry1 is locked to cycle only between the hydroquinone and neutral semiquinone states when UV-damaged DNA is present. Other potential substrates, including undamaged DNA and ATP, have no discernible effect on the electrochemistry, and the kinetics of the reduction is unaffected by damaged DNA. Binding of the damaged DNA substrate determines the role of the protein and prevents the presumed photochemistry required for blue-light signaling.
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Affiliation(s)
- Yvonne M Gindt
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, New Jersey 07043, United States
| | - Adriana Messyasz
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, New Jersey 07043, United States
| | - Pamela I Jumbo
- Department of Chemistry and Biochemistry, Montclair State University, Montclair, New Jersey 07043, United States
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10
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Paulus B, Bajzath C, Melin F, Heidinger L, Kromm V, Herkersdorf C, Benz U, Mann L, Stehle P, Hellwig P, Weber S, Schleicher E. Spectroscopic characterization of radicals and radical pairs in fruit fly cryptochrome - protonated and nonprotonated flavin radical-states. FEBS J 2015; 282:3175-89. [PMID: 25879256 DOI: 10.1111/febs.13299] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/21/2015] [Accepted: 04/14/2015] [Indexed: 01/05/2023]
Abstract
Drosophila melanogaster cryptochrome is one of the model proteins for animal blue-light photoreceptors. Using time-resolved and steady-state optical spectroscopy, we studied the mechanism of light-induced radical-pair formation and decay, and the photoreduction of the FAD cofactor. Exact kinetics on a microsecond to minutes timescale could be extracted for the wild-type protein using global analysis. The wild-type exhibits a fast photoreduction reaction from the oxidized FAD to the FAD(•-) state with a very positive midpoint potential of ~ +125 mV, although no further reduction could be observed. We could also demonstrate that the terminal tryptophan of the conserved triad, W342, is directly involved in electron transfer; however, photoreduction could not be completely inhibited in a W342F mutant. The investigation of another mutation close to the FAD cofactor, C416N, rather unexpectedly reveals accumulation of a protonated flavin radical on a timescale of several seconds. The obtained data are critically discussed with the ones obtained from another protein, Escherichia coli photolyase, and we conclude that the amino acid opposite N(5) of the isoalloxazine moiety of FAD is able to (de)stabilize the protonated FAD radical but not to significantly modulate the kinetics of any light-inducted reactions.
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Affiliation(s)
- Bernd Paulus
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Csaba Bajzath
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Frédéric Melin
- Laboratoire de Bioélectrochimie et Spectroscopie Université de Strasbourg, France
| | - Lorenz Heidinger
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Viktoria Kromm
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | | | - Ulrike Benz
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Lisa Mann
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Patricia Stehle
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Petra Hellwig
- Laboratoire de Bioélectrochimie et Spectroscopie Université de Strasbourg, France
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Germany
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Migliore A, Polizzi NF, Therien M, Beratan DN. Biochemistry and theory of proton-coupled electron transfer. Chem Rev 2014; 114:3381-465. [PMID: 24684625 PMCID: PMC4317057 DOI: 10.1021/cr4006654] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Indexed: 02/01/2023]
Affiliation(s)
- Agostino Migliore
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Nicholas F. Polizzi
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Michael
J. Therien
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - David N. Beratan
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
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Matsubara T, Araida N, Hayashi D, Yamada H. Computational Study on the Mechanism of the Electron-Transfer-Induced Repair of the (6–4) T–T Photoproduct of DNA by Photolyase: Possibility of a Radical Cation Pathway. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2014. [DOI: 10.1246/bcsj.20130298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
| | - Nozomi Araida
- Department of Chemistry, Faculty of Science, Kanagawa University
| | - Daichi Hayashi
- Department of Chemistry, Faculty of Science, Kanagawa University
| | - Hatsumi Yamada
- Department of Chemistry, Faculty of Science, Kanagawa University
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13
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Bernini C, Andruniów T, Olivucci M, Pogni R, Basosi R, Sinicropi A. Effects of the Protein Environment on the Spectral Properties of Tryptophan Radicals in Pseudomonas aeruginosa Azurin. J Am Chem Soc 2013; 135:4822-33. [DOI: 10.1021/ja400464n] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Caterina Bernini
- Dipartimento di Biotecnologie,
Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Tadeusz Andruniów
- Quantum Chemistry and Molecular
Modelling Lab, Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wyb. Wyspianskiego
27, 50-370 Wroclaw, Poland
| | - Massimo Olivucci
- Dipartimento di Biotecnologie,
Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy
- Chemistry Department, Bowling Green State University, Bowling Green, Ohio
43403, United States
| | - Rebecca Pogni
- Dipartimento di Biotecnologie,
Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Riccardo Basosi
- Dipartimento di Biotecnologie,
Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Adalgisa Sinicropi
- Dipartimento di Biotecnologie,
Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy
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Schrauben JN, Cattaneo M, Day TC, Tenderholt AL, Mayer JM. Multiple-site concerted proton-electron transfer reactions of hydrogen-bonded phenols are nonadiabatic and well described by semiclassical Marcus theory. J Am Chem Soc 2012; 134:16635-45. [PMID: 22974135 PMCID: PMC3476473 DOI: 10.1021/ja305668h] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Photo-oxidations of hydrogen-bonded phenols using excited-state polyarenes are described to derive fundamental understanding of multiple-site concerted proton-electron transfer reactions (MS-CPET). Experiments have examined phenol bases having -CPh(2)NH(2), -Py, and -CH(2)Py groups ortho to the phenol hydroxyl group and tert-butyl groups in the 4,6-positions for stability (HOAr-NH(2), HOAr-Py, and HOAr-CH(2)Py, respectively; Py = pyridyl; Ph = phenyl). The photo-oxidations proceed by intramolecular proton transfer from the phenol to the pendent base concerted with electron transfer to the excited polyarene. For comparison, 2,4,6-(t)Bu(3)C(6)H(2)OH, a phenol without a pendent base and tert-butyl groups in the 2,4,6-positions, has also been examined. Many of these bimolecular reactions are fast, with rate constants near the diffusion limit. Combining the photochemical k(CPET) values with those from prior thermal stopped-flow kinetic studies gives data sets for the oxidations of HOAr-NH(2) and HOAr-CH(2)Py that span over 10(7) in k(CPET) and nearly 0.9 eV in driving force (ΔG(o)'). Plots of log(k(CPET)) vs ΔG(o)', including both excited-state anthracenes and ground state aminium radical cations, define a single Marcus parabola in each case. These two data sets are thus well described by semiclassical Marcus theory, providing a strong validation of the use of this theory for MS-CPET. The parabolas give λ(CPET) ≅ 1.15-1.2 eV and H(ab) ≅ 20-30 cm(-1). These experiments represent the most direct measurements of H(ab) for MS-CPET reactions to date. Although rate constants are available only up to the diffusion limit, the parabolas clearly peak well below the adiabatic limit of ca. 6 × 10(12) s(-1). Thus, this is a very clear demonstration that the reactions are nonadiabatic. The nonadiabatic character slows the reactions by a factor of ~45. Results for the oxidation of HOAr-Py, in which the phenol and base are conjugated, and for oxidation of 2,4,6-(t)Bu(3)C(6)H(2)OH, which lacks a base, show that both have substantially lower λ and larger pre-exponential terms. The implications of these results for MS-CPET reactions are discussed.
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Affiliation(s)
| | | | - Thomas C. Day
- Department of Chemistry, University of Washington, Seattle WA 98195
| | | | - James M. Mayer
- Department of Chemistry, University of Washington, Seattle WA 98195
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15
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Ohzu S, Ishizuka T, Hirai Y, Jiang H, Sakaguchi M, Ogura T, Fukuzumi S, Kojima T. Mechanistic insight into catalytic oxidations of organic compounds by ruthenium(iv)-oxo complexes with pyridylamine ligands. Chem Sci 2012. [DOI: 10.1039/c2sc21195e] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Bonin J, Robert M. Photoinduced Proton-Coupled Electron Transfers in Biorelevant Phenolic Systems. Photochem Photobiol 2011; 87:1190-203. [DOI: 10.1111/j.1751-1097.2011.00996.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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