101
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Nakanishi T, Hori Y, Wu S, Sato H, Okazawa A, Kojima N, Horie Y, Okajima H, Sakamoto A, Shiota Y, Yoshizawa K, Sato O. Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006763] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Takumi Nakanishi
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
| | - Yuta Hori
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
- Center for Computational Sciences University of Tsukuba Tsukuba 305-8577 Japan
| | - Shuqi Wu
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
| | - Hiroyasu Sato
- Rigaku Corporation 3-9-12 Matsubaracho Akishima Tokyo 196-8666 Japan
| | - Atsushi Okazawa
- Department of Basic Science Graduation School of Arts and Sciences The University of Tokyo 3-8-1 Komaba, Meguro-ku Tokyo 153-8902 Japan
- Current address: Division of Chemistry Institution of Liberal Education Nihon University School of Medicine 30-1 Oyaguchi Uemachi Itabashi-ku Tokyo 173-8610 Japan
| | - Norimichi Kojima
- Department of Basic Science Graduation School of Arts and Sciences The University of Tokyo 3-8-1 Komaba, Meguro-ku Tokyo 153-8902 Japan
| | - Yusuke Horie
- Graduate School of Science and Engineering Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara Kanagawa 252-5258 Japan
| | - Hajime Okajima
- Graduate School of Science and Engineering Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara Kanagawa 252-5258 Japan
| | - Akira Sakamoto
- Graduate School of Science and Engineering Aoyama Gakuin University 5-10-1 Fuchinobe, Chuo-ku Sagamihara Kanagawa 252-5258 Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
| | - Osamu Sato
- Institute for Materials Chemistry and Engineering & IRCCS Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan
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102
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Tsui E, Metrano AJ, Tsuchiya Y, Knowles RR. Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer. Angew Chem Int Ed Engl 2020; 59:11845-11849. [PMID: 32227658 PMCID: PMC7451027 DOI: 10.1002/anie.202003959] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 03/28/2020] [Indexed: 12/22/2022]
Abstract
We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII -based photoredox catalyst, a Brønsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O-H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
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Affiliation(s)
- Elaine Tsui
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Anthony J Metrano
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Yuto Tsuchiya
- 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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103
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Kaur M, Kaur B, Kaur J, Kaur A, Bhatti R, Singh P. Role of water in cyclooxygenase catalysis and design of anti-inflammatory agents targeting two sites of the enzyme. Sci Rep 2020; 10:10764. [PMID: 32612190 PMCID: PMC7329864 DOI: 10.1038/s41598-020-67655-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 06/12/2020] [Indexed: 11/15/2022] Open
Abstract
While designing the anti-inflammatory agents targeting cyclooxygenase-2 (COX-2), we first identified a water loop around the heme playing critical role in the enzyme catalysis. The results of molecular dynamic studies supported by the strong hydrogen-bonding equilibria of the participating atoms, radical stabilization energies, the pKa of the H-donor/acceptor sites and the cyclooxygenase activity of pertinent muCOX-2 ravelled the working of the water–peptide channel for coordinating the flow of H·/electron between the heme and Y385. Based on the working of H·/electron transfer channel between the 12.5 Å distant radical generation and the radical disposal sites, a series of molecules was designed and synthesized. Among this category of compounds, an appreciably potent anti-inflammatory agent exhibiting IC50 0.06 μM against COX-2 and reversing the formalin induced analgesia and carageenan induced inflammation in mice by 90% was identified. Further it was revealed that, justifying its bidentate design, the compound targets water loop (heme bound site) and the arachidonic acid binding pockets of COX-2.
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Affiliation(s)
- Manpreet Kaur
- UGC Sponsored Centre for Advanced Studies, Department of Chemistry, Guru Nanak Dev University, Amritsar, 143005, India
| | - Baljit Kaur
- UGC Sponsored Centre for Advanced Studies, Department of Chemistry, Guru Nanak Dev University, Amritsar, 143005, India
| | - Jagroop Kaur
- UGC Sponsored Centre for Advanced Studies, Department of Chemistry, Guru Nanak Dev University, Amritsar, 143005, India
| | - Anudeep Kaur
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India
| | - Rajbir Bhatti
- Department of Pharmaceutical Sciences, Guru Nanak Dev University, Amritsar, 143005, India
| | - Palwinder Singh
- UGC Sponsored Centre for Advanced Studies, Department of Chemistry, Guru Nanak Dev University, Amritsar, 143005, India.
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104
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Brugh AM, Forbes MDE. Anomalous chemically induced electron spin polarization in proton-coupled electron transfer reactions: insight into radical pair dynamics. Chem Sci 2020; 11:6268-6274. [PMID: 32953022 PMCID: PMC7480077 DOI: 10.1039/d0sc02691c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 05/27/2020] [Indexed: 11/21/2022] Open
Abstract
Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has been used to study the proton coupled electron transfer (PCET) reaction between a ruthenium complex (Ru(bpz)(bpy)2) and several substituted hydroquinones (HQ). After excitation at 355 nm, the HQ moiety forms a strong hydrogen bond to the exposed N atoms in the bpz heterocycle. At some point afterwards, a PCET reaction takes place in which an electron from the O atom of the hydrogen bond transfers to the metal center, and the proton forming the hydrogen bond remains on the bpz ligand N atom. The result is a semiquinone radical (HQ˙), whose TREPR spectrum is strongly polarized by the triplet mechanism (TM) of chemically induced dynamic electron spin polarization (CIDEP). Closer examination of the CIDEP pattern reveals, in some cases, a small amount of radical pair mechanism (RPM) polarization. We hypothesize that when the HQ moiety has electron donating groups (EDGs) substituted on the ring, S-T- RPM polarization is observed in HQ˙. These anomalous intensities are accounted for by spectral simulation using polarization from S-T- mixing. The generation of S-T- RPM is attributed to slow radical separation after PCET due to stabilization of the positive charge on the ring by EDGs. Results from a temperature dependence support the hypothesis.
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Affiliation(s)
- Alexander M Brugh
- Department of Chemistry , Center for Photochemical Sciences , Bowling Green State University , Bowling Green , OH 43403 , USA .
| | - Malcolm D E Forbes
- Department of Chemistry , Center for Photochemical Sciences , Bowling Green State University , Bowling Green , OH 43403 , USA .
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105
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Nilsen-Moe A, Reinhardt CR, Glover SD, Liang L, Hammes-Schiffer S, Hammarström L, Tommos C. Proton-Coupled Electron Transfer from Tyrosine in the Interior of a de novo Protein: Mechanisms and Primary Proton Acceptor. J Am Chem Soc 2020; 142:11550-11559. [PMID: 32479070 PMCID: PMC7315633 DOI: 10.1021/jacs.0c04655] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
![]()
Proton-coupled
electron transfer (PCET) from tyrosine produces
a neutral tyrosyl radical (Y•) that is vital to
many catalytic redox reactions. To better understand how the protein
environment influences the PCET properties of tyrosine, we have studied
the radical formation behavior of Y32 in the α3Y model protein. The previously solved α3Y solution NMR structure shows that Y32 is sequestered
∼7.7 ± 0.3 Å below the protein surface without any
primary proton acceptors nearby. Here we present transient absorption
kinetic data and molecular dynamics (MD) simulations to resolve the
PCET mechanism associated with Y32 oxidation. Y32• was generated in a bimolecular reaction with
[Ru(bpy)3]3+ formed by flash photolysis. At
pH > 8, the rate constant of Y32• formation
(kPCET) increases by one order of magnitude
per pH unit, corresponding to a proton-first mechanism via tyrosinate
(PTET). At lower pH < 7.5, the pH dependence is weak and shows
a previously measured KIE ≈ 2.5, which best fits a concerted
mechanism. kPCET is independent of phosphate
buffer concentration at pH 6.5. This provides clear evidence that
phosphate buffer is not the primary proton acceptor. MD simulations
show that one to two water molecules can enter the hydrophobic cavity
of α3Y and hydrogen bond to Y32, as well
as the possibility of hydrogen-bonding interactions between Y32 and E13, through structural fluctuations that
reorient surrounding side chains. Our results illustrate how protein
conformational motions can influence the redox reactivity of a tyrosine
residue and how PCET mechanisms can be tuned by changing the pH even
when the PCET occurs within the interior of a protein.
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Affiliation(s)
- Astrid Nilsen-Moe
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, Uppsala 75120, Sweden
| | - Clorice R Reinhardt
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Starla D Glover
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, Uppsala 75120, Sweden
| | - Li Liang
- Departments of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, United States
| | | | - Leif Hammarström
- Department of Chemistry, Ångström Laboratory, Uppsala University, Box 523, Uppsala 75120, Sweden
| | - Cecilia Tommos
- Departments of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, United States.,Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, United States
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106
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Bím D, Chalupský J, Culka M, Solomon EI, Rulíšek L, Srnec M. Proton-Electron Transfer to the Active Site Is Essential for the Reaction Mechanism of Soluble Δ 9-Desaturase. J Am Chem Soc 2020; 142:10412-10423. [PMID: 32406236 DOI: 10.1021/jacs.0c01786] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A full understanding of the catalytic action of non-heme iron (NHFe) and non-heme diiron (NHFe2) enzymes is still beyond the grasp of contemporary computational and experimental techniques. Many of these enzymes exhibit fascinating chemo-, regio-, and stereoselectivity, in spite of employing highly reactive intermediates which are necessary for activations of most stable chemical bonds. Herein, we study in detail one intriguing representative of the NHFe2 family of enzymes: soluble Δ9 desaturase (Δ9D), which desaturates rather than performing the thermodynamically favorable hydroxylation of substrate. Its catalytic mechanism has been explored in great detail by using QM(DFT)/MM and multireference wave function methods. Starting from the spectroscopically observed 1,2-μ-peroxo diferric P intermediate, the proton-electron uptake by P is the favored mechanism for catalytic activation, since it allows a significant reduction of the barrier of the initial (and rate-determining) H-atom abstraction from the stearoyl substrate as compared to the "proton-only activated" pathway. Also, we ruled out that a Q-like intermediate (high-valent diamond-core bis-μ-oxo-[FeIV]2 unit) is involved in the reaction mechanism. Our mechanistic picture is consistent with the experimental data available for Δ9D and satisfies fairly stringent conditions required by Nature: the chemo-, stereo-, and regioselectivity of the desaturation of stearic acid. Finally, the mechanisms evaluated are placed into a broader context of NHFe2 chemistry, provided by an amino acid sequence analysis through the families of the NHFe2 enzymes. Our study thus represents an important contribution toward understanding the catalytic action of the NHFe2 enzymes and may inspire further work in NHFe(2) biomimetic chemistry.
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Affiliation(s)
- Daniel Bím
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 182 23, Czech Republic.,Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, Prague 6 166 10, Czech Republic
| | - Jakub Chalupský
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, Prague 6 166 10, Czech Republic
| | - Martin Culka
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, Prague 6 166 10, Czech Republic
| | - Edward I Solomon
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305-5080, United States
| | - Lubomír Rulíšek
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám. 2, Prague 6 166 10, Czech Republic
| | - Martin Srnec
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8 182 23, Czech Republic
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107
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Tsui E, Metrano AJ, Tsuchiya Y, Knowles RR. Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton‐Coupled Electron Transfer. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202003959] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Elaine Tsui
- Department of Chemistry Princeton University Princeton NJ 08544 USA
| | | | - Yuto Tsuchiya
- Department of Chemistry Princeton University Princeton NJ 08544 USA
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108
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Kang G, Taguchi AT, Stubbe J, Drennan CL. Structure of a trapped radical transfer pathway within a ribonucleotide reductase holocomplex. Science 2020; 368:424-427. [PMID: 32217749 DOI: 10.1126/science.aba6794] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 03/16/2020] [Indexed: 12/27/2022]
Abstract
Ribonucleotide reductases (RNRs) are a diverse family of enzymes that are alone capable of generating 2'-deoxynucleotides de novo and are thus critical in DNA biosynthesis and repair. The nucleotide reduction reaction in all RNRs requires the generation of a transient active site thiyl radical, and in class I RNRs, this process involves a long-range radical transfer between two subunits, α and β. Because of the transient subunit association, an atomic resolution structure of an active α2β2 RNR complex has been elusive. We used a doubly substituted β2, E52Q/(2,3,5)-trifluorotyrosine122-β2, to trap wild-type α2 in a long-lived α2β2 complex. We report the structure of this complex by means of cryo-electron microscopy to 3.6-angstrom resolution, allowing for structural visualization of a 32-angstrom-long radical transfer pathway that affords RNR activity.
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Affiliation(s)
- Gyunghoon Kang
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge MA, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Alexander T Taguchi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA, USA
| | - JoAnne Stubbe
- Department of Biology, Massachusetts Institute of Technology, Cambridge MA, USA. .,Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA, USA
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge MA, USA. .,Department of Biology, Massachusetts Institute of Technology, Cambridge MA, USA.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA, USA
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109
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Ranya S, Ananth N. Multistate ring polymer instantons and nonadiabatic reaction rates. J Chem Phys 2020; 152:114112. [DOI: 10.1063/1.5132807] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Srinath Ranya
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Nandini Ananth
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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110
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Ji T, Chen XY, Huang L, Rueping M. Remote Trifluoromethylthiolation Enabled by Organophotocatalytic C-C Bond Cleavage. Org Lett 2020; 22:2579-2583. [PMID: 32176516 DOI: 10.1021/acs.orglett.0c00493] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The first metal-free ring opening/trifluoromethylthiolation of cycloalkanols for the formation of remote C(sp3)-SCF3 bonds has been developed. A variety of trifluoromethylthiolated carbonyl compounds that are otherwise difficult to achieve were prepared in good yields under mild reaction conditions. The reaction is assumed to proceed via C-C bond cleavage of the alkoxyl radical species generated via a photoredox-enabled intramolecular proton-coupled electron transfer process, followed by trifluoromethylthiolation of the resulting C-centered radical with the N-(trifluoromethylthio)phthalimide reagent.
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Affiliation(s)
- Tengfei Ji
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Xiang-Yu Chen
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Long Huang
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
| | - Magnus Rueping
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany.,KAUST Catalysis Center (KCC), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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111
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Swords WB, Meyer GJ, Hammarström L. Excited-state proton-coupled electron transfer within ion pairs. Chem Sci 2020; 11:3460-3473. [PMID: 34109019 PMCID: PMC8152629 DOI: 10.1039/c9sc04941j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The use of light to drive proton-coupled electron transfer (PCET) reactions has received growing interest, with recent focus on the direct use of excited states in PCET reactions (ES-PCET). Electrostatic ion pairs provide a scaffold to reduce reaction orders and have facilitated many discoveries in electron-transfer chemistry. Their use, however, has not translated to PCET. Herein, we show that ion pairs, formed solely through electrostatic interactions, provide a general, facile means to study an ES-PCET mechanism. These ion pairs formed readily between salicylate anions and tetracationic ruthenium complexes in acetonitrile solution. Upon light excitation, quenching of the ruthenium excited state occurred through ES-PCET oxidation of salicylate within the ion pair. Transient absorption spectroscopy identified the reduced ruthenium complex and oxidized salicylate radical as the primary photoproducts of this reaction. The reduced reaction order due to ion pairing allowed the first-order PCET rate constants to be directly measured through nanosecond photoluminescence spectroscopy. These PCET rate constants saturated at larger driving forces consistent with approaching the Marcus barrierless region. Surprisingly, a proton-transfer tautomer of salicylate, with the proton localized on the carboxylate functional group, was present in acetonitrile. A pre-equilibrium model based on this tautomerization provided non-adiabatic electron-transfer rate constants that were well described by Marcus theory. Electrostatic ion pairs were critical to our ability to investigate this PCET mechanism without the need to covalently link the donor and acceptor or introduce specific hydrogen bonding sites that could compete in alternate PCET pathways.
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Affiliation(s)
- Wesley B Swords
- Department of Chemistry, Ångström Laboratories, Uppsala University Box 523 SE75120 Uppsala Sweden .,Department of Chemistry, University of North Carolina at Chapel Hill Chapel Hill 27599 USA
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill Chapel Hill 27599 USA
| | - Leif Hammarström
- Department of Chemistry, Ångström Laboratories, Uppsala University Box 523 SE75120 Uppsala Sweden
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112
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Lee H, Jang HS, Cho DH, Lee J, Seong B, Kang G, Park YS, Nam KT, Lee YS, Byun D. Redox-Active Tyrosine-Mediated Peptide Template for Large-Scale Single-Crystalline Two-Dimensional Silver Nanosheets. ACS NANO 2020; 14:1738-1744. [PMID: 31999426 DOI: 10.1021/acsnano.9b07392] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Although self-assembly of various peptides has been widely applied, it is challenging to obtain single-crystalline and layer-by-layered nanostructures in a two-dimensional system. Here, we report a method for controlling the morphology and crystal growth at room temperature by a redox-active peptide template that can specifically co-assemble with metal ions. During the crystal growth, a silver ion-coordinated α-helical peptide (+3HN-YYACAYY-COO-) induces long-range atomic ordering at the air/water interface, which leads to multilayered single-crystalline silver nanosheets without an additional annealing process. Furthermore, this peptide template can facilitate efficient electron transfer between the independent metal nanosheets to improve electrochemical properties. We expect that this peptide template-based single-crystal growth method can be extended to synthesize other materials.
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Affiliation(s)
- Hyungdong Lee
- Department of Mechanical Engineering , Sungkyunkwan University , Jangan-gu, Suwon-si , Gyeonggi-do , Republic of Korea 16419
| | - Hyung-Seok Jang
- ZTI Biosciences, Inc. , Gangnam-gu, Seoul , Republic of Korea 06325
| | - Dae-Hyun Cho
- Department of Mechatronics , Gyeongnam National University of Science and Technology , Jinju-si , Gyeongsangnam-do , Republic of Korea 52725
| | - Jaehyun Lee
- Department of Mechanical Engineering , Sungkyunkwan University , Jangan-gu, Suwon-si , Gyeonggi-do , Republic of Korea 16419
| | - Baekhoon Seong
- Department of Mechanical Engineering , Sungkyunkwan University , Jangan-gu, Suwon-si , Gyeonggi-do , Republic of Korea 16419
| | - Giho Kang
- Department of Mechanical Engineering , Sungkyunkwan University , Jangan-gu, Suwon-si , Gyeonggi-do , Republic of Korea 16419
| | - Yong-Sun Park
- ZTI Biosciences, Inc. , Gangnam-gu, Seoul , Republic of Korea 06325
- Department of Material Science and Engineering , Seoul National University , Gwanak-gu, Seoul , Republic of Korea 08826
| | - Ki Tae Nam
- Department of Material Science and Engineering , Seoul National University , Gwanak-gu, Seoul , Republic of Korea 08826
| | - Yoon-Sik Lee
- School of Chemical and Biological Engineering , Seoul National University , Gwanak-gu, Seoul , Republic of Korea 08826
| | - Doyoung Byun
- Department of Mechanical Engineering , Sungkyunkwan University , Jangan-gu, Suwon-si , Gyeonggi-do , Republic of Korea 16419
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113
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Kadam K, Khole VV, Ghosalkar K, Jagtap D, Yarramala DS, Ramachandran B. Thiol based mechanism internalises interacting partners to outer dense fibers in sperm. Free Radic Biol Med 2020; 148:170-181. [PMID: 31923584 DOI: 10.1016/j.freeradbiomed.2019.12.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 12/04/2019] [Accepted: 12/23/2019] [Indexed: 11/19/2022]
Abstract
The sperm tail outer dense fibres (ODFs) contribute passive structural role in sperm motility. The level of disulphide cross-linking of ODFs and their structural thickness determines flagellar bending curvature and motility. During epididymal maturation, proteins are internalized to modify ODF disulphide cross-linking and enable motility. Sperm thiol status is further altered during capacitation in female tract. This suggests that components in female reproductive tract acting on thiol/disulphides could be capable of modulating the tail stiffness to facilitate modulation of the sperm tail rigidity and waveform en route to fertilization. Understanding the biochemical properties and client proteins of ODFs in reproductive tract fluids will help bridge this gap. Using recombinant ODF2 (aka Testis Specific Antigen of 70 kDa) as bait, we identified client proteins in male and female reproductive fluids. A thiol-based interaction and internalization indicates sperm can harness reproductive tract fluids for proteins that interact with ODFs and likely modulate the tail stiffness en route to fertilization.
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Affiliation(s)
- Kaushiki Kadam
- Department of Gamete Immunobiology, National Institute for Research in Reproductive Health, J.M Street, Parel, Mumbai, 400012, India.
| | - Vrinda V Khole
- Department of Gamete Immunobiology, National Institute for Research in Reproductive Health, J.M Street, Parel, Mumbai, 400012, India
| | - Kanaka Ghosalkar
- Department of Gamete Immunobiology, National Institute for Research in Reproductive Health, J.M Street, Parel, Mumbai, 400012, India
| | - Dhanashree Jagtap
- Structural Biology Department, National Institute for Research in Reproductive Health, J.M Street, Parel, Mumbai, 400012, India
| | - Deepthi S Yarramala
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
| | - Bini Ramachandran
- Thermo Fisher Scientific India Pvt. Ltd, 403-404, Delphi 'B' Wing, Hiranandani Business Park, Powai, Mumbai, 400076, India
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114
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Leitch JA, Rossolini T, Rogova T, Maitland JAP, Dixon DJ. α-Amino Radicals via Photocatalytic Single-Electron Reduction of Imine Derivatives. ACS Catal 2020. [DOI: 10.1021/acscatal.9b05011] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Jamie A. Leitch
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Thomas Rossolini
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Tatiana Rogova
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - J. Andrew P. Maitland
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Darren J. Dixon
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
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115
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Offenbacher AR, Barry BA. A Proton Wire Mediates Proton Coupled Electron Transfer from Hydroxyurea and Other Hydroxamic Acids to Tyrosyl Radical in Class Ia Ribonucleotide Reductase. J Phys Chem B 2020; 124:345-354. [PMID: 31904962 DOI: 10.1021/acs.jpcb.9b08587] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton-coupled electron transfer (PCET) is fundamental to many important biological reactions, including solar energy conversion and DNA synthesis. For example, class Ia ribonucleotide reductases (RNRs) contain a tyrosyl radical-diiron cofactor with one aspartate ligand, D84. The tyrosyl radical, Y122•, in the β2 subunit acts as a radical initiator and oxidizes an active site cysteine in the α2 subunit. A transient quaternary α2/β2 complex is induced by substrate and effector binding. The hydroxamic acid, hydroxyurea (HU), reduces Y122• in a PCET reaction involving an electron and proton. This reaction is associated with the loss of activity, a conformational change at Y122, and a change in hydrogen bonding to the Fe1 ligand, D84. Here, we use isotopic labeling, solvent isotope exchange, proton inventories, and reaction-induced Fourier transform infrared (RIFT-IR) spectroscopy to show that the PCET reactions of hydroxamic acids are associated with a characteristic spectrum, which is assignable to electrostatic changes at nonligating aspartate residues. Notably, RIFT-IR spectroscopy reveals this characteristic spectrum when the effects of HU, hydroxylamine, and N-methylhydroxylamine are compared. A large solvent isotope effect is observed for each of the hydroxamic acid reactions, and proton inventories predict that the reactions are associated with the transfer of multiple protons in the transition state. The reduction of Y122• with 4-methoxyphenol does not lead to these characteristic carboxylate shifts and is associated with only a small solvent isotope effect. In addition to studies of the effects of hydroxamic acids on β2 alone, the reactions involving the quaternary α2β2 complex were also investigated. HU treatment of the quaternary complex, α2/β2/ATP/CDP, leads to a similar carboxylate shift spectrum, as observed with β2 alone. The use of globally labeled 13C chimeras (13C α2, 13C β2) confirms the assignment. Because the spectrum is sensitive to 13C β2 labeling, but not 13C α2 labeling, the quaternary complex spectrum is assigned to electrostatic changes in β2 carboxylate groups. Examination of the β2 X-ray structure reveals a hydrogen-bonded network leading from the protein surface to Y122. This predicted network includes nonligating aspartates, glutamate ligands to the iron cluster, and predicted crystallographically resolved water molecules. The network is similar when class Ia RNR structures from Escherichia coli, human, and mouse are compared. We propose that the PCET reactions of hydroxamic acids are mediated by a hydrogen-bonded proton wire in the β2 subunit.
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Affiliation(s)
- Adam R Offenbacher
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,Department of Chemistry , East Carolina University , Greenville , North Carolina 27858 , United States
| | - Bridgette A Barry
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
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116
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Sakaushi K. Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms. Phys Chem Chem Phys 2020; 22:11219-11243. [DOI: 10.1039/d0cp01052a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The fundamental aspects of quantum electrocatalysts are discussed together with the newly developed electrochemical kinetic isotope effect (EC-KIE) approach.
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Affiliation(s)
- Ken Sakaushi
- Center for Green Research on Energy and Environmental Materials
- National Institute for Materials Science
- Tsukuba
- Japan
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117
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Ju M, Cho OH, Lee J, Namgung SD, Song MK, Balamurugan M, Kwon JY, Nam KT. Quantitative analysis of the coupling between proton and electron transport in peptide/manganese oxide hybrid films. Phys Chem Chem Phys 2020; 22:7537-7545. [DOI: 10.1039/c9cp05581a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A novel platform is proposed to quantify the coupling phenomenon between electrons and protons in tyrosine-rich peptide/manganese oxide hybrid films at room temperature.
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Affiliation(s)
- Misong Ju
- Department of Materials Science and Engineering
- Seoul National University
- Seoul
- South Korea
| | - Ouk Hyun Cho
- Department of Materials Science and Engineering
- Seoul National University
- Seoul
- South Korea
| | - Jaehun Lee
- Department of Materials Science and Engineering
- Seoul National University
- Seoul
- South Korea
| | - Seok Daniel Namgung
- School of Integrated Technology
- Yonsei University
- Incheon
- South Korea
- Yonsei Institute of Convergence Technology
| | - Min-Kyu Song
- School of Integrated Technology
- Yonsei University
- Incheon
- South Korea
- Yonsei Institute of Convergence Technology
| | - Mani Balamurugan
- Department of Materials Science and Engineering
- Seoul National University
- Seoul
- South Korea
| | - Jang-Yeon Kwon
- School of Integrated Technology
- Yonsei University
- Incheon
- South Korea
- Yonsei Institute of Convergence Technology
| | - Ki Tae Nam
- Department of Materials Science and Engineering
- Seoul National University
- Seoul
- South Korea
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118
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Fukuzumi S, Cho KB, Lee YM, Hong S, Nam W. Mechanistic dichotomies in redox reactions of mononuclear metal–oxygen intermediates. Chem Soc Rev 2020; 49:8988-9027. [DOI: 10.1039/d0cs01251c] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This review article focuses on various mechanistic dichotomies in redox reactions of metal–oxygen intermediates with the emphasis on understanding and controlling their redox reactivity from experimental and theoretical points of view.
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Affiliation(s)
- Shunichi Fukuzumi
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Korea
- Graduate School of Science and Engineering
| | - Kyung-Bin Cho
- Department of Chemistry
- Jeonbuk National University
- Jeonju 54896
- Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Korea
| | - Seungwoo Hong
- Department of Chemistry
- Sookmyung Women's University
- Seoul 04310
- Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Korea
- School of Chemistry and Chemical Engineering
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119
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Karković Marković A, Jakobušić Brala C, Pilepić V, Uršić S. Hydrogen Tunnelling as a Probe of the Involvement of Water Vibrational Dynamics in Aqueous Chemistry? Molecules 2019; 25:E172. [PMID: 31906197 PMCID: PMC6983115 DOI: 10.3390/molecules25010172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 12/14/2019] [Accepted: 12/28/2019] [Indexed: 11/17/2022] Open
Abstract
Our study of tunnelling in proton-coupled electron transfer (PCET) oxidation of ascorbate with hexacyanoferrate(III) follows the insights obtained from ultrafast 2D IR spectroscopy and theoretical studies of the vibrational water dynamics that led to the proposal of the involvement of collective intermolecular excitonic vibrational water dynamics in aqueous chemistry. To test the proposal, the hydrogen tunnelling modulation observed in the PCET reaction studied in the presence of low concentrations of various partial hydrophobic solutes in the water reaction system has been analyzed in terms of the proposed involvement of the collective intermolecular vibrational water dynamics in activation process in the case. The strongly linear correlation between common tunnelling signatures, isotopic values of Arrhenius prefactor ratios ln AH/AD and isotopic differences in activation enthalpies ΔΔH‡ (H,D) observed in the process in fairly diluted water solutions containing various partial hydrophobic solutes (such as dioxane, acetonitrile, ethanol, and quaternary ammonium ions) points to the common physical origin of the phenomenon in all the cases. It is suggested that the phenomenon can be rooted in an interplay of delocalized collective intermolecular vibrational dynamics of water correlated with vibrations of the coupled transition configuration, where the donor-acceptor oscillations, the motions being to some degree along the reaction coordinate, lead to modulation of hydrogen tunnelling in the reaction.
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Affiliation(s)
| | - Cvijeta Jakobušić Brala
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10 000 Zagreb, Croatia; (A.K.M.); (V.P.)
| | | | - Stanko Uršić
- Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10 000 Zagreb, Croatia; (A.K.M.); (V.P.)
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120
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Sayfutyarova ER, Hammes-Schiffer S. Substituent Effects on Photochemistry of Anthracene-Phenol-Pyridine Triads Revealed by Multireference Calculations. J Am Chem Soc 2019; 142:487-494. [PMID: 31846322 DOI: 10.1021/jacs.9b11425] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Inverted region behavior for concerted proton-coupled electron transfer (PCET) was recently demonstrated for biomimetic anthracene-phenol-pyridine molecular triads. Photoexcitation of the anthracene to a locally excited state (LES) is followed by concerted electron transfer from the phenol to the anthracene and proton transfer from the phenol to the pyridine, forming a relatively long-lived charge separated state (CSS). The long-lived CSS and the inverted region behavior associated with the decay from the CSS to the ground state through charge recombination were experimentally observed only for triads with certain substituents on the anthracene and the pyridine. To explain this distinction, we computed the proton potential energy curves in four substituted triads using the complete active space self-consistent-field method and multireference perturbation theory, including solvent effects with a dielectric continuum model. The calculations revealed a local electron-proton transfer (LEPT) state, in which both the electron and proton transfer from the phenol to the pyridine. When the LEPT state is lower in energy than the CSS, it may provide an alternative pathway for fast decay from the LES to the ground state and thereby preclude detection of the CSS and the inverted region behavior. These calculations predict that substituents stabilizing negative charge on the pyridine and destabilizing negative charge on the anthracene will favor the LEPT pathway, while substituents with the reverse effects will favor the CSS pathway, which could exhibit inverted region behavior. These insights about the stabilization of energy-storing charge-separated states have implications for designing and controlling PCET reactions in artificial photosynthetic systems and other energy conversion processes.
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Affiliation(s)
- Elvira R Sayfutyarova
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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121
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Wild U, Hübner O, Himmel H. Redox-Active Guanidines in Proton-Coupled Electron-Transfer Reactions: Real Alternatives to Benzoquinones? Chemistry 2019; 25:15988-15992. [PMID: 31535741 PMCID: PMC7065378 DOI: 10.1002/chem.201903438] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Indexed: 01/24/2023]
Abstract
Guanidino-functionalized aromatics (GFAs) are readily available, stable organic redox-active compounds. In this work we apply one particular GFA compound, 1,2,4,5-tetrakis(tetramethylguanidino)benzene, in its oxidized form in a variety of oxidation/oxidative coupling reactions to demonstrate the scope of its proton-coupled electron transfer (PCET) reactivity. Addition of an excess of acid boosts its oxidation power, enabling the oxidative coupling of substrates with redox potentials of at least +0.77 V vs. Fc+ /Fc. The green recyclability by catalytic re-oxidation with dioxygen is also shown. Finally, a direct comparison indicates that GFAs are real alternatives to toxic halo- or cyano-substituted benzoquinones.
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Affiliation(s)
- Ute Wild
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Olaf Hübner
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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122
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Biswas S, Bhattacharya I, Chakraborty T. Identification of an Emitting Metastable State of p-Fluorophenol-Ammonia 1:2 Complex by Laser-Induced Fluorescence Spectroscopy. J Phys Chem A 2019; 123:10563-10570. [PMID: 31714082 DOI: 10.1021/acs.jpca.9b07958] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have demonstrated here, for the first time to our knowledge, the formation of an emitting metastable species upon lowest electronic excitation (S1) of a hydrogen-bonded 1:2 complex of para-fluorophenol (pFP) with ammonia (NH3), which is known to be one of the smallest reactive complexes to undergo excited state H-atom transfer (HAT) reaction to produce •NH4(NH3) radical fragment. The emission spectrum of the species is characterized to be red-shifted, broad, and structureless. From the viewpoint of energy balance, an excited state proton transfer (ESPT) is unfavorable, but according to predicted electronic structure parameters, the metastable state species could be stabilized by charge transfer (CT) interaction at the hydrogen-bonded geometry of the complex. We propose that this species could act as an intermediate to the HAT process in the excited state. The observation of such a state could be valuable to understand the complex dynamics of similar events in biologically relevant systems.
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Affiliation(s)
- Souvick Biswas
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
| | - Indrani Bhattacharya
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
| | - Tapas Chakraborty
- School of Chemical Sciences , Indian Association for the Cultivation of Science , 2A Raja S C Mullick Road, Jadavpur , Kolkata 700032 , India
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123
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Maldonado-Domínguez M, Bím D, Fučík R, Čurík R, Srnec M. Reactive mode composition factor analysis of transition states: the case of coupled electron-proton transfers. Phys Chem Chem Phys 2019; 21:24912-24918. [PMID: 31690920 DOI: 10.1039/c9cp05131g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A simple method for the evaluation of the kinetic energy distribution within the reactive mode of a transition state (TS), denoted as the Reactive Mode Composition Factor (RMCF), is presented. It allows one to directly map the barrier properties onto the atomic-motion components of the reaction coordinate at the TS, which has potential to shed light onto some mechanistic features of a chemical process. To demonstrate the applicability of RMCF to reactivity, we link the kinetic energy distribution within a reactive mode with the asynchronicity (η) in C-H bond activation, as they both evolve in a series of coupled proton-electron transfer (CPET) reactions between FeIVO oxidants and 1,4-cyclohexadiene. RMCF shows how the earliness or lateness of a process manifests as a redistribution of kinetic energy in the reactive mode as a function of the free energy of reaction (ΔG0) and η. Finally, the title analysis can be applied to predict H-atom tunneling contributions and kinetic isotope effects in a set of reactions, yielding a transparent rationalization based on the kinetic energy distributions in the reactive mode.
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Affiliation(s)
- Mauricio Maldonado-Domínguez
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
| | - Daniel Bím
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic. and Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague 6, 16610, Czech Republic
| | - Radek Fučík
- Department of Mathematics, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 12000 Praha 2, Czech Republic
| | - Roman Čurík
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
| | - Martin Srnec
- J. Heyrovský Institute of Physical Chemistry, The Czech Academy of Sciences, Dolejškova 3, Prague 8, 18223, Czech Republic.
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124
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Yee EF, Dzikovski B, Crane BR. Tuning Radical Relay Residues by Proton Management Rescues Protein Electron Hopping. J Am Chem Soc 2019; 141:17571-17587. [PMID: 31603693 DOI: 10.1021/jacs.9b05715] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Transient tyrosine and tryptophan radicals play key roles in the electron transfer (ET) reactions of photosystem (PS) II, ribonucleotide reductase (RNR), photolyase, and many other proteins. However, Tyr and Trp are not functionally interchangeable, and the factors controlling their reactivity are often unclear. Cytochrome c peroxidase (CcP) employs a Trp191•+ radical to oxidize reduced cytochrome c (Cc). Although a Tyr191 replacement also forms a stable radical, it does not support rapid ET from Cc. Here we probe the redox properties of CcP Y191 by non-natural amino acid substitution, altering the ET driving force and manipulating the protic environment of Y191. Higher potential fluorotyrosine residues increase ET rates marginally, but only addition of a hydrogen bond donor to Tyr191• (via Leu232His or Glu) substantially alters activity by increasing the ET rate by nearly 30-fold. ESR and ESEEM spectroscopies, crystallography, and pH-dependent ET kinetics provide strong evidence for hydrogen bond formation to Y191• by His232/Glu232. Rate measurements and rapid freeze quench ESR spectroscopy further reveal differences in radical propagation and Cc oxidation that support an increased Y191• formal potential of ∼200 mV in the presence of E232. Hence, Y191 inactivity results from a potential drop owing to Y191•+ deprotonation. Incorporation of a well-positioned base to accept and donate back a hydrogen bond upshifts the Tyr• potential into a range where it can effectively oxidize Cc. These findings have implications for the YZ/YD radicals of PS II, hole-hopping in RNR and cryptochrome, and engineering proteins for long-range ET reactions.
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Affiliation(s)
- Estella F Yee
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Boris Dzikovski
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States.,National Biomedical Center for Advanced ESR Technologies (ACERT) , Cornell University , Ithaca , New York 14850 , United States
| | - Brian R Crane
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
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125
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Liu T, Tyburski R, Wang S, Fernández-Terán R, Ott S, Hammarström L. Elucidating Proton-Coupled Electron Transfer Mechanisms of Metal Hydrides with Free Energy- and Pressure-Dependent Kinetics. J Am Chem Soc 2019; 141:17245-17259. [PMID: 31587555 DOI: 10.1021/jacs.9b08189] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proton-coupled electron transfer (PCET) was studied in a series of tungsten hydride complexes with pendant pyridyl arms ([(PyCH2Cp)WH(CO)3], PyCH2Cp = pyridylmethylcyclopentadienyl), triggered by laser flash-generated RuIII-tris-bipyridine oxidants, in acetonitrile solution. The free energy dependence of the rate constant and the kinetic isotope effects (KIEs) showed that the PCET mechanism could be switched between concerted and the two stepwise PCET mechanisms (electron-first or proton-first) in a predictable fashion. Straightforward and general guidelines for how the relative rates of the different mechanisms depend on oxidant and base are presented. The rate of the concerted reaction should depend symmetrically on changes in oxidant and base strength, that is on the overall ΔG0PCET, and we argue that an "asynchronous" behavior would not be consistent with a model where the electron and proton tunnel from a common transition state. The observed rate constants and KIEs were examined as a function of hydrostatic pressure (1-2000 bar) and were found to exhibit qualitatively different dependence on pressure for different PCET mechanisms. This is discussed in terms of different volume profiles of the PCET mechanisms as well as enhanced proton tunneling for the concerted mechanism. The results allowed for assignment of the main mechanism operating in the different cases, which is one of the critical questions in PCET research. They also show how the rate of a PCET reaction will be affected very differently by changes of oxidant and base strength, depending on which mechanism dominates. This is of fundamental interest as well as of practical importance for rational design of, for example, catalysts for fuel cells and solar fuel formation, which operate in steps of PCET reactions. The mechanistic richness shown by this system illustrates that the specific mechanism is not intrinsic to a specific synthetic catalyst or enzyme active site but depends on the reaction conditions.
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Affiliation(s)
- Tianfei Liu
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
| | - Robin Tyburski
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
| | - Shihuai Wang
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
| | - Ricardo Fernández-Terán
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
| | - Sascha Ott
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
| | - Leif Hammarström
- Department of Chemistry, Ångström Laboratory , Uppsala University , Box 532, SE-751 20 Uppsala , Sweden
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126
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Walter P, Kaifer E, Herrmann H, Wadepohl H, Hübner O, Himmel H. Redox‐Active Guanidines with One or Two Guanidino Groups and Their Integration in Low‐Dimensional Perovskite Structures. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900975] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Petra Walter
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Elisabeth Kaifer
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hendrik Herrmann
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hubert Wadepohl
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Olaf Hübner
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hans‐Jörg Himmel
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
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127
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Church MS, Ananth N. Semiclassical dynamics in the mixed quantum-classical limit. J Chem Phys 2019; 151:134109. [PMID: 31594341 DOI: 10.1063/1.5117160] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The semiclassical double Herman-Kluk initial value representation is an accurate approach to computing quantum real time correlation functions, but its applications are limited by the need to evaluate an oscillatory integral. In previous work, we have shown that this "sign problem" can be mitigated using the modified Filinov filtration technique to control the extent to which individual modes of the system contribute to the overall phase of the integrand. Here, we follow this idea to a logical conclusion: we analytically derive a general expression for the mixed quantum-classical limit of the semiclassical correlation function-analytical mixed quantum-classical-initial value representation (AMQC-IVR), where the phase contributions from the "classical" modes of the system are filtered while the "quantum" modes are treated in the full semiclassical limit. We numerically demonstrate the accuracy and efficiency of the AMQC-IVR formulation in calculations of quantum correlation functions and reaction rates using three model systems with varied coupling strengths between the classical and quantum subsystems. We also introduce a separable prefactor approximation that further reduces computational cost but is only accurate in the limit of weak coupling between the quantum and classical subsystems.
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Affiliation(s)
- Matthew S Church
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Nandini Ananth
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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128
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Nazemi A, Cundari TR. Computational Analysis of Proton-Coupled Electron Transfer in Hydrotris(triazolyl)borate Mid–Late 3d and 4d Transition Metal Complexes. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00322] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Azadeh Nazemi
- Department of Chemistry, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States
| | - Thomas R. Cundari
- Department of Chemistry, Center of Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States
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129
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Kaila VRI. Long-range proton-coupled electron transfer in biological energy conversion: towards mechanistic understanding of respiratory complex I. J R Soc Interface 2019; 15:rsif.2017.0916. [PMID: 29643224 PMCID: PMC5938582 DOI: 10.1098/rsif.2017.0916] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/13/2018] [Indexed: 12/20/2022] Open
Abstract
Biological energy conversion is driven by efficient enzymes that capture, store and transfer protons and electrons across large distances. Recent advances in structural biology have provided atomic-scale blueprints of these types of remarkable molecular machinery, which together with biochemical, biophysical and computational experiments allow us to derive detailed energy transduction mechanisms for the first time. Here, I present one of the most intricate and least understood types of biological energy conversion machinery, the respiratory complex I, and how its redox-driven proton-pump catalyses charge transfer across approximately 300 Å distances. After discussing the functional elements of complex I, a putative mechanistic model for its action-at-a-distance effect is presented, and functional parallels are drawn to other redox- and light-driven ion pumps.
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Affiliation(s)
- Ville R I Kaila
- Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, Garching, Germany
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130
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Nakanishi T, Hori Y, Sato H, Wu SQ, Okazawa A, Kojima N, Yamamoto T, Einaga Y, Hayami S, Horie Y, Okajima H, Sakamoto A, Shiota Y, Yoshizawa K, Sato O. Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex. J Am Chem Soc 2019; 141:14384-14393. [PMID: 31422661 DOI: 10.1021/jacs.9b07204] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.
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Affiliation(s)
- Takumi Nakanishi
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan
| | - Yuta Hori
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan.,Center for Computational Sciences , University of Tsukuba , Tsukuba 305-8577 , Japan
| | - Hiroyasu Sato
- Rigaku Corporation , 3-9-12 Matsubaracho , Akishima , Tokyo 196-8666 , Japan
| | - Shu-Qi Wu
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan
| | - Atsushi Okazawa
- Department of Basic Science, Graduation School of Arts and Sciences , The University of Tokyo , 3-8-1 Komaba , Meguro-ku , Tokyo 153-8902 , Japan
| | - Norimichi Kojima
- Toyota Physical and Chemical Research Institute , Yokomichi, Nagakute , Aichi 480-1192 , Japan
| | - Takashi Yamamoto
- Department of Chemistry, Faculty of Science and Technology , Keio University , 3-14-1 Hiyoshi, Kohoku-ku , Yokohama , Kanagawa 223-8522 , Japan
| | - Yasuaki Einaga
- Department of Chemistry, Faculty of Advanced Science and Technology , Kumamoto University , 2-39-1 Kurokami, Chuo-ku , Kumamoto 860-8555 , Japan
| | - Shinya Hayami
- Department of Chemistry, Faculty of Advanced Science and Technology , Kumamoto University , 2-39-1 Kurokami, Chuo-ku , Kumamoto 860-8555 , Japan.,Institute of Pulsed Power Science (IPPS) , Kumamoto University , 2-39-1 Kurokami , Chuo-ku, Kumamoto 860-8555 , Japan
| | - Yusuke Horie
- Graduate School of Science and Engineering , Aoyama Gakuin University , 5-10-1 Fuchinobe, Chuo-ku , Sagamihara , Kanagawa 252-5258 , Japan
| | - Hajime Okajima
- Graduate School of Science and Engineering , Aoyama Gakuin University , 5-10-1 Fuchinobe, Chuo-ku , Sagamihara , Kanagawa 252-5258 , Japan
| | - Akira Sakamoto
- Graduate School of Science and Engineering , Aoyama Gakuin University , 5-10-1 Fuchinobe, Chuo-ku , Sagamihara , Kanagawa 252-5258 , Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan
| | - Osamu Sato
- Institute for Materials Chemistry and Engineering & IRCCS , Kyushu University , 744 Motooka, Nishi-ku , Fukuoka 819-0395 , Japan
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131
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Caron A, Morin É, Collins SK. Bifunctional Copper-Based Photocatalyst for Reductive Pinacol-Type Couplings. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01718] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Antoine Caron
- Département de Chimie, Centre for Green Chemistry and Catalysis, Université de Montréal, 6128 Station Downtown, Montréal, Québec H3C 3J7, Canada
| | - Émilie Morin
- Département de Chimie, Centre for Green Chemistry and Catalysis, Université de Montréal, 6128 Station Downtown, Montréal, Québec H3C 3J7, Canada
| | - Shawn K. Collins
- Département de Chimie, Centre for Green Chemistry and Catalysis, Université de Montréal, 6128 Station Downtown, Montréal, Québec H3C 3J7, Canada
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132
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Jackson MN, Kaminsky CJ, Oh S, Melville JF, Surendranath Y. Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis. J Am Chem Soc 2019; 141:14160-14167. [PMID: 31353897 PMCID: PMC6748662 DOI: 10.1021/jacs.9b04981] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The efficient interconversion
of electrical and chemical energy
requires the intimate coupling of electrons and small-molecule substrates
at catalyst active sites. In molecular electrocatalysis, the molecule
acts as a redox mediator which typically undergoes oxidation or reduction
in a separate step from substrate activation. These mediated pathways
introduce a high-energy intermediate, cap the driving force for substrate
activation at the reduction potential of the molecule, and impede
access to high rates at low overpotentials. Here we show that electronically
coupling a molecular hydrogen evolution catalyst to a graphitic electrode
eliminates stepwise pathways and forces concerted electron transfer
and proton binding. Electrochemical and X-ray absorption spectroscopy
data establish that hydrogen evolution catalysis at the graphite-conjugated
Rh molecule proceeds without first reducing the metal center. These
results have broad implications for the molecular-level design of
energy conversion catalysts.
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Affiliation(s)
- Megan N Jackson
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Corey J Kaminsky
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Seokjoon Oh
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Jonathan F Melville
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Yogesh Surendranath
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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133
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Enomoto T, Kondo M, Masaoka S. Proton-Coupled Electron Transfer Induced by Near-Infrared Light. Chem Asian J 2019; 14:2806-2809. [PMID: 31290247 DOI: 10.1002/asia.201900863] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Indexed: 11/06/2022]
Abstract
A proton-coupled electron transfer reaction induced by near-infrared light (>710 nm) has been achieved using a dye that shows intense NIR absorption property and electron/proton-accepting abilities. The developed system generated long-lived radical species and showed high reversibility and robustness. Mechanistic investigations suggested that the rate-determining step of the reaction involves the proton transfer process.
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Affiliation(s)
- Takafumi Enomoto
- Department of Life and Coordination-Complex Molecular Science, Institution for Molecular Science (IMS), 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan
| | - Mio Kondo
- Department of Life and Coordination-Complex Molecular Science, Institution for Molecular Science (IMS), 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.,Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shigeyuki Masaoka
- Department of Life and Coordination-Complex Molecular Science, Institution for Molecular Science (IMS), 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.,Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
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134
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Odella E, Wadsworth BL, Mora SJ, Goings JJ, Huynh MT, Gust D, Moore TA, Moore GF, Hammes-Schiffer S, Moore AL. Proton-Coupled Electron Transfer Drives Long-Range Proton Translocation in Bioinspired Systems. J Am Chem Soc 2019; 141:14057-14061. [DOI: 10.1021/jacs.9b06978] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Emmanuel Odella
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Brian L. Wadsworth
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - S. Jimena Mora
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Joshua J. Goings
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Mioy T. Huynh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Devens Gust
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Thomas A. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Gary F. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Ana L. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
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135
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Thongyod W, Buranachai C, Pengpan T, Punwong C. Fluorescence quenching by photoinduced electron transfer between 7-methoxycoumarin and guanine base facilitated by hydrogen bonds: an in silico study. Phys Chem Chem Phys 2019; 21:16258-16269. [PMID: 31304496 DOI: 10.1039/c9cp02037c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this study, the effects of hydrogen bond (H-bond) formation on fluorescence quenching of 7-methoxycoumarin (7MC) via photo-induced electron transfer from a guanine base (Gua) are investigated using a combined quantum mechanics/molecular mechanics simulation. The electronic structure is calculated by the floating occupation molecular orbital complete active space configuration interaction modification on a semiempirical method. Then the full multiple spawning method is employed for the dynamics simulations on multiple electronic states. The methods employed here are validated by simulating direct dynamics of 7MC (without Gua) and compared with available experimental results. Our computational results are in good agreement with the previously reported experimental results in terms of spectroscopic properties of 7MC. In the case of a H-bonded 7MC-Gua complex, the results from constrained dynamics simulations and single-point calculations suggest that the electron transfer occurs on the second excited state and it depends not only on the H-bond length but also on the intermolecular planarity between 7MC and Gua. Moreover, a proton coupled electron transfer can occur at ≈1 Å of H-bond length, where a proton from Gua is also transferred together with the electron to 7MC. The obtained simulations are expected to be greatly beneficial for designing effective fluorescently labeled nucleotide probes as well as providing information for precise fluorescence signal interpretation.
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Affiliation(s)
- Wutthinan Thongyod
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand. and Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Songkhla 90112, Thailand
| | - Chittanon Buranachai
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand. and Center of Excellence for Trace Analysis and Biosensor, Prince of Songkla University, Songkhla 90112, Thailand
| | - Teparksorn Pengpan
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand.
| | - Chutintorn Punwong
- Department of Physics, Faculty of Science, Prince of Songkla University, Songkhla 90112, Thailand.
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136
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Maróti P. Thermodynamic View of Proton Activated Electron Transfer in the Reaction Center of Photosynthetic Bacteria. J Phys Chem B 2019; 123:5463-5473. [PMID: 31181159 DOI: 10.1021/acs.jpcb.9b03506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The temperature dependence of the sequential coupling of proton transfer to the second interquinone electron transfer is studied in the reaction center proteins of photosynthetic bacteria modified by different mutations and treatment by divalent cations. The Eyring plots of kinetics were evaluated by the Marcus theory of electron and proton transfer. In mutants of electron transfer limitation (including the wild type), the observed thermodynamic parameters had to be corrected for those of the fast proton pre-equilibrium. The electron transfer is nonadiabatic with transmission coefficient 6 × 10-4, and the reorganization energy amounts to 1.2 eV. If the proton transfer is the rate limiting step, the reorganization energy and the works terms fall in the range of 200-500 meV, depending on the site of damage in the proton transfer chain. The product term is 100-150 meV larger than the reactant term. While the electron transfer mutants have a low free energy of activation (∼200 meV), the proton transfer variants show significantly elevated levels of the free energy barrier (∼500 meV). The second electron transfer in the bacterial reaction center can serve as a model system of coupled electron and proton transfer in other proteins or ion channels.
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Affiliation(s)
- Péter Maróti
- Institute of Medical Physics , University of Szeged , Rerrich Béla tér 1 , Szeged , H-6720 , Hungary
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137
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Darcy JW, Kolmar SS, Mayer JM. Transition State Asymmetry in C-H Bond Cleavage by Proton-Coupled Electron Transfer. J Am Chem Soc 2019; 141:10777-10787. [PMID: 31199137 DOI: 10.1021/jacs.9b04303] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The selective transformation of C-H bonds is a longstanding challenge in modern chemistry. A recent report details C-H oxidation via multiple-site concerted proton-electron transfer (MS-CPET), where the proton and electron in the C-H bond are transferred to separate sites. Reactivity at a specific C-H bond was achieved by appropriate positioning of an internal benzoate base. Here, we extend that report to reactions of a series of molecules with differently substituted fluorenyl-benzoates and varying outer-sphere oxidants. These results probe the fundamental rate versus driving force relationships in this MS-CPET reaction at carbon by separately modulating the driving force for the proton and electron transfer components. The rate constants depend strongly on the pKa of the internal base, but depend much less on the nature of the outer-sphere oxidant. These observations suggest that the transition states for these reactions are imbalanced. Density functional theory (DFT) was used to generate an internal reaction coordinate, which qualitatively reproduced the experimental observation of a transition state imbalance. Thus, in this system, homolytic C-H bond cleavage involves concerted but asynchronous transfer of the H+ and e-. The nature of this transfer has implications for synthetic methodology and biological systems.
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Affiliation(s)
- Julia W Darcy
- Department of Chemistry , Yale University , New Haven , Connecticut 06520-8107 , United States
| | - Scott S Kolmar
- Department of Chemistry , Yale University , New Haven , Connecticut 06520-8107 , United States
| | - James M Mayer
- Department of Chemistry , Yale University , New Haven , Connecticut 06520-8107 , United States
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138
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Ashida Y, Arashiba K, Tanaka H, Egi A, Nakajima K, Yoshizawa K, Nishibayashi Y. Molybdenum-Catalyzed Ammonia Formation Using Simple Monodentate and Bidentate Phosphines as Auxiliary Ligands. Inorg Chem 2019; 58:8927-8932. [DOI: 10.1021/acs.inorgchem.9b01340] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
| | | | - Hiromasa Tanaka
- School of Liberal Arts and Sciences, Daido University, Minami-ku, Nagoya 457-8530, Japan
| | - Akihito Egi
- Institute for Materials Chemistry and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
| | | | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan
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139
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Jackson M, Pegis ML, Surendranath Y. Graphite-Conjugated Acids Reveal a Molecular Framework for Proton-Coupled Electron Transfer at Electrode Surfaces. ACS CENTRAL SCIENCE 2019; 5:831-841. [PMID: 31139719 PMCID: PMC6535968 DOI: 10.1021/acscentsci.9b00114] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Indexed: 05/21/2023]
Abstract
Proton-coupled electron-transfer (PCET) steps play a key role in energy conversion reactions. Molecular PCET reactions are well-described by "square schemes" in which the overall thermochemistry of the reaction is broken into its constituent proton-transfer and electron-transfer components. Although this description has been essential for understanding molecular PCET, no such framework exists for PCET reactions that take place at electrode surfaces. Herein, we develop a molecular square scheme framework for interfacial PCET by investigating the electrochemistry of molecularly well-defined acid/base sites conjugated to graphitic electrodes. Using cyclic voltammetry, we first demonstrate that, irrespective of the redox properties of the corresponding molecular analogue, proton transfer to graphite-conjugated acid/base sites is coupled to electron transfer. We then show that the thermochemistry of surface PCET events can be described by the pK a of the molecular analogue and the potential of zero free charge (zero-field reduction potential) of the electrode. This work provides a general framework for analyzing and predicting the thermochemistry of interfacial PCET reactions.
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140
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Hickey DP, Minteer SD. Coupling Theory to Electrode Design for Electrocatalysis. ACS CENTRAL SCIENCE 2019; 5:745-746. [PMID: 31139708 PMCID: PMC6535775 DOI: 10.1021/acscentsci.9b00387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
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141
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Kim D, Rahaman SMW, Mercado BQ, Poli R, Holland PL. Roles of Iron Complexes in Catalytic Radical Alkene Cross-Coupling: A Computational and Mechanistic Study. J Am Chem Soc 2019; 141:7473-7485. [PMID: 31025567 PMCID: PMC6953484 DOI: 10.1021/jacs.9b02117] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A growing and useful class of alkene coupling reactions involve hydrogen atom transfer (HAT) from a metal-hydride species to an alkene to form a free radical, which is responsible for subsequent bond formation. Here, we use a combination of experimental and computational investigations to map out the mechanistic details of iron-catalyzed reductive alkene cross-coupling, an important representative of the HAT alkene reactions. We are able to explain several observations that were previously mysterious. First, the rate-limiting step in the catalytic cycle is the formation of the reactive Fe-H intermediate, elucidating the importance of the choice of reductant. Second, the success of the catalytic system is attributable to the exceptionally weak (17 kcal/mol) Fe-H bond, which performs irreversible HAT to alkenes in contrast to previous studies on isolable hydride complexes where this addition was reversible. Third, the organic radical intermediates can reversibly form organometallic species, which helps to protect the free radicals from side reactions. Fourth, the previously accepted quenching of the postcoupling radical through stepwise electron transfer/proton transfer is not as favorable as alternative mechanisms. We find that there are two feasible pathways. One uses concerted proton-coupled electron transfer (PCET) from an iron(II) ethanol complex, which is facilitated because the O-H bond dissociation free energy is lowered by 30 kcal/mol upon metal binding. In an alternative pathway, an O-bound enolate-iron(III) complex undergoes proton shuttling from an iron-bound alcohol. These kinetic, spectroscopic, and computational studies identify key organometallic species and PCET steps that control selectivity and reactivity in metal-catalyzed HAT alkene coupling, and create a firm basis for elucidation of mechanisms in the growing class of HAT alkene cross-coupling reactions.
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Affiliation(s)
- Dongyoung Kim
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - S. M. Wahidur Rahaman
- LCC-CNRS, Université de Toulouse, INPT, 205 Route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Rinaldo Poli
- LCC-CNRS, Université de Toulouse, INPT, 205 Route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
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142
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Nguyen ST, Zhu Q, Knowles RR. PCET-Enabled Olefin Hydroamidation Reactions with N-Alkyl Amides. ACS Catal 2019; 9:4502-4507. [PMID: 32292642 DOI: 10.1021/acscatal.9b00966] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Olefin aminations are important synthetic technologies for the construction of aliphatic C-N bonds. Here we report a catalytic protocol for olefin hydroamidation that proceeds through transient amidyl radical intermediates that are formed via proton-coupled electron transfer (PCET) activation of the strong N-H bonds in N-alkyl amides by an excited-state iridium photocatalyst and a dialkyl phosphate base. This method exhibits a broad substrate scope, high functional group tolerance, and amenability to use in cascade polycyclization reactions. The feasibility of this PCET protocol in enabling the intermolecular anti-Markovnikov hydroamidation reactions of unactivated olefins is also demonstrated.
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Affiliation(s)
- Suong T. Nguyen
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Qilei Zhu
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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143
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Reguera G. Microbial nanowires and electroactive biofilms. FEMS Microbiol Ecol 2019; 94:5000162. [PMID: 29931163 DOI: 10.1093/femsec/fiy086] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 05/11/2018] [Indexed: 12/14/2022] Open
Abstract
Geobacter bacteria are the only microorganisms known to produce conductive appendages or pili to electronically connect cells to extracellular electron acceptors such as iron oxide minerals and uranium. The conductive pili also promote cell-cell aggregation and the formation of electroactive biofilms. The hallmark of these electroactive biofilms is electronic heterogeneity, mediated by coordinated interactions between the conductive pili and matrix-associated cytochromes. Collectively, the matrix-associated electron carriers discharge respiratory electrons from cells in multilayered biofilms to electron-accepting surfaces such as iron oxide coatings and electrodes poised at a metabolically oxidizable potential. The presence of pilus nanowires in the electroactive biofilms also promotes the immobilization and reduction of soluble metals, even when present at toxic concentrations. This review summarizes current knowledge about the composition of the electroactive biofilm matrix and the mechanisms that allow the wired Geobacter biofilms to generate electrical currents and participate in metal redox transformations.
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Affiliation(s)
- Gemma Reguera
- Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
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144
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Parada GA, Goldsmith ZK, Kolmar S, Pettersson Rimgard B, Mercado BQ, Hammarström L, Hammes-Schiffer S, Mayer JM. Concerted proton-electron transfer reactions in the Marcus inverted region. Science 2019; 364:471-475. [PMID: 30975771 DOI: 10.1126/science.aaw4675] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/28/2019] [Indexed: 11/02/2022]
Abstract
Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.
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Affiliation(s)
| | | | - Scott Kolmar
- Department of Chemistry, Yale University, New Haven, CT, USA
| | | | | | - Leif Hammarström
- Department of Chemistry - Ångström Laboratory, Uppsala University, Uppsala, Sweden.
| | | | - James M Mayer
- Department of Chemistry, Yale University, New Haven, CT, USA.
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145
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Bezdek MJ, Chirik PJ. Pyridine(diimine) Chelate Hydrogenation in a Molybdenum Nitrido Ethylene Complex. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00095] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J. Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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146
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McCaslin TG, Pagba CV, Chi SH, Hwang HJ, Gumbart JC, Perry JW, Olivieri C, Porcelli F, Veglia G, Guo Z, McDaniel M, Barry BA. Structure and Function of Tryptophan-Tyrosine Dyads in Biomimetic β Hairpins. J Phys Chem B 2019; 123:2780-2791. [PMID: 30888824 PMCID: PMC6463897 DOI: 10.1021/acs.jpcb.8b12452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
![]()
Tyrosine–tryptophan (YW) dyads
are ubiquitous
structural motifs in enzymes and play roles in proton-coupled electron
transfer (PCET) and, possibly, protection from oxidative stress. Here,
we describe the function of YW dyads in de novo designed 18-mer, β
hairpins. In Peptide M, a YW dyad is formed between W14 and Y5. A
UV hypochromic effect and an excitonic Cotton signal are observed,
in addition to singlet, excited state (W*) and fluorescence emission
spectral shifts. In a second Peptide, Peptide MW, a Y5–W13
dyad is formed diagonally across the strand and distorts the backbone.
On a picosecond timescale, the W* excited-state decay kinetics are
similar in all peptides but are accelerated relative to amino acids
in solution. In Peptide MW, the W* spectrum is consistent with increased
conformational flexibility. In Peptide M and MW, the electron paramagnetic
resonance spectra obtained after UV photolysis are characteristic
of tyrosine and tryptophan radicals at 160 K. Notably, at pH 9, the
radical photolysis yield is decreased in Peptide M and MW, compared
to that in a tyrosine and tryptophan mixture. This protective effect
is not observed at pH 11 and is not observed in peptides containing
a tryptophan–histidine dyad or tryptophan alone. The YW dyad
protective effect is attributed to an increase in the radical recombination
rate. This increase in rate can be facilitated by hydrogen-bonding
interactions, which lower the barrier for the PCET reaction at pH
9. These results suggest that the YW dyad structural motif promotes
radical quenching under conditions of reactive oxygen stress.
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Affiliation(s)
| | | | | | | | | | | | | | - Fernando Porcelli
- Department for Innovation in Biological, Agro-Food and Forest Systems , University of Tuscia , 01100 Viterbo , Italy
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147
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Wagner C, Hübner O, Kaifer E, Himmel HJ. Probing the Proton-Coupled Electron-Transfer (PCET) Reactivity of a Cross-Conjugated Cruciform Chromophore by Redox-State-Dependent Fluorescence. Chemistry 2019; 25:3781-3785. [PMID: 30688382 DOI: 10.1002/chem.201900268] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Indexed: 11/07/2022]
Abstract
Proton-coupled electron transfer (PCET) reactions are of great importance in synthetic chemistry and in biology, but the acquisition of kinetic information for these reactions is often difficult. Herein, we report the synthesis of a new PCET reagent, showing redox-state dependent fluorescence, by merging the concept of cross-conjugated cruciform chromophores with the strategy of imposing redox activity and Brønsted basicity to aromatic compounds by substitution with guanidino groups. The compound is isolated and characterized in all stable states-reduced, twofold and fourfold protonated and twofold oxidized-and then applied in PCET reactions by using its redox-state dependent fluorescence signal for kinetic measurements.
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Affiliation(s)
- Conrad Wagner
- Anorganisch-Chemisches Institut, Ruprecht-Karls-University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Olaf Hübner
- Anorganisch-Chemisches Institut, Ruprecht-Karls-University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut, Ruprecht-Karls-University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Anorganisch-Chemisches Institut, Ruprecht-Karls-University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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148
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Lee J, Ju M, Cho OH, Kim Y, Nam KT. Tyrosine-Rich Peptides as a Platform for Assembly and Material Synthesis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2019; 6:1801255. [PMID: 30828522 PMCID: PMC6382316 DOI: 10.1002/advs.201801255] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 09/27/2018] [Indexed: 05/27/2023]
Abstract
The self-assembly of biomolecules can provide a new approach for the design of functional systems with a diverse range of hierarchical nanoarchitectures and atomically defined structures. In this regard, peptides, particularly short peptides, are attractive building blocks because of their ease of establishing structure-property relationships, their productive synthesis, and the possibility of their hybridization with other motifs. Several assembling peptides, such as ionic-complementary peptides, cyclic peptides, peptide amphiphiles, the Fmoc-peptide, and aromatic dipeptides, are widely studied. Recently, studies on material synthesis and the application of tyrosine-rich short peptide-based systems have demonstrated that tyrosine units serve as not only excellent assembly motifs but also multifunctional templates. Tyrosine has a phenolic functional group that contributes to π-π interactions for conformation control and efficient charge transport by proton-coupled electron-transfer reactions in natural systems. Here, the critical roles of the tyrosine motif with respect to its electrochemical, chemical, and structural properties are discussed and recent discoveries and advances made in tyrosine-rich short peptide systems from self-assembled structures to peptide/inorganic hybrid materials are highlighted. A brief account of the opportunities in design optimization and the applications of tyrosine peptide-based biomimetic materials is included.
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Affiliation(s)
- Jaehun Lee
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Misong Ju
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Ouk Hyun Cho
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Younghye Kim
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
| | - Ki Tae Nam
- Department of Materials Science and EngineeringSeoul National UniversitySeoul08826Republic of Korea
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149
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Ota E, Wang H, Frye NL, Knowles RR. A Redox Strategy for Light-Driven, Out-of-Equilibrium Isomerizations and Application to Catalytic C-C Bond Cleavage Reactions. J Am Chem Soc 2019; 141:1457-1462. [PMID: 30628777 DOI: 10.1021/jacs.8b12552] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We report a general protocol for the light-driven isomerization of cyclic aliphatic alcohols to linear carbonyl compounds. These reactions proceed via proton-coupled electron-transfer activation of alcohol O-H bonds followed by subsequent C-C β-scission of the resulting alkoxy radical intermediates. In many cases, these redox-neutral isomerizations proceed in opposition to a significant energetic gradient, yielding products that are less thermodynamically stable than the starting materials. A mechanism is presented to rationalize this out-of-equilibrium behavior that may serve as a model for the design of other contrathermodynamic transformations driven by excited-state redox events.
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Affiliation(s)
- Eisuke Ota
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Huaiju Wang
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Nils Lennart Frye
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
| | - Robert R Knowles
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
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150
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Pannwitz A, Wenger OS. Proton-coupled multi-electron transfer and its relevance for artificial photosynthesis and photoredox catalysis. Chem Commun (Camb) 2019; 55:4004-4014. [DOI: 10.1039/c9cc00821g] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Photoinduced PCET meets catalysis, and the accumulation of multiple redox equivalents is of key importance.
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Affiliation(s)
- Andrea Pannwitz
- Department of Chemistry
- University of Basel
- 4056 Basel
- Switzerland
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