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Fedunov RG, Pozdnyakov IP, Mikheylis AV, Melnikov AA, Chekalin SV, Glebov EM. Primary photophysical and photochemical processes for cerium ammonium nitrate (CAN) in acetonitrile. Photochem Photobiol Sci 2024; 23:781-792. [PMID: 38546955 DOI: 10.1007/s43630-024-00554-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 02/12/2024] [Indexed: 04/16/2024]
Abstract
Cerium ammonium nitrate (CAN) is an important photolytic source of NO3• radicals in aqueous nitric acid solutions and in acetonitrile. In this work we performed the study of primary photochemical processes for CAN in acetonitrile by means of ultrafast TA spectroscopy and quantum chemical calculations. Photoexcitation of CAN is followed by ultrafast (< 100 fs) intersystem crossing; the vibrationally cooled triplet state decays to pentacoordinated Ce(III) intermediate and NO3• radical with the characteristic time of ca. 40 ps. Quantum chemical (QM) calculations satisfactorily describe the UV-vis spectrum of the triplet state. An important feature of CAN photochemistry in CH3CN is the partial stabilization of the radical complex (RC) [(NH4)2CeIII(NO3)5…NO3•], which lifetime is ca. 2 μs. The possibility of the RC stabilization is supported by the QM calculations.
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Affiliation(s)
- Roman G Fedunov
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., 630090, Novosibirsk, Russian Federation
- Novosibirsk State University, 2 Pirogova Str., 630090, Novosibirsk, Russian Federation
| | - Ivan P Pozdnyakov
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., 630090, Novosibirsk, Russian Federation
| | - Aleksander V Mikheylis
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., 630090, Novosibirsk, Russian Federation
| | - Alexei A Melnikov
- Institute of Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya Str., Troitsk, 119333, Moscow, Russian Federation
| | - Sergei V Chekalin
- Institute of Spectroscopy, Russian Academy of Sciences, 5 Fizicheskaya Str., Troitsk, 119333, Moscow, Russian Federation
| | - Evgeni M Glebov
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., 630090, Novosibirsk, Russian Federation.
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Grivin VP, Matveeva SG, Fedunov RG, Yanshole VV, Vasilchenko DB, Glebov EM. Photochemistry of (n-Bu 4N) 2[Pt(NO 3) 6] in acetonitrile. Photochem Photobiol Sci 2024; 23:747-755. [PMID: 38430371 DOI: 10.1007/s43630-024-00550-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Accepted: 02/08/2024] [Indexed: 03/03/2024]
Abstract
Photochemistry of the (n-Bu4N)2[Pt(NO3)6] complex in acetonitrile was studied by means of stationary photolysis and nanosecond laser flash photolysis. The primary photochemical process was found to be an intramolecular electron transfer followed by an escape of an •NO3 radical to the solution bulk. The spectra of two successive Pt(III) intermediates were detected in the microsecond time domain, and their spectral and kinetic characteristics were determined. These intermediates were identified as PtIII(NO3)52- and PtIII(NO3)4- complexes. Disproportionation of Pt(III) species resulted in formation of final Pt(II) products.
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Affiliation(s)
- Vjacheslav P Grivin
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str, 630090, Novosibirsk, Russian Federation
| | - Svetlana G Matveeva
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str, 630090, Novosibirsk, Russian Federation
| | - Roman G Fedunov
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str, 630090, Novosibirsk, Russian Federation
| | - Vadim V Yanshole
- International Tomography Center, Siberian Branch of the Russian Academy of Sciences, 3a Institutskaya Str., 630090, Novosibirsk, Russian Federation
- Novosibirsk State University, 2 Pirogova Str., 630090, Novosibirsk, Russian Federation
| | - Danila B Vasilchenko
- A.V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str, 630090, Novosibirsk, Russian Federation
| | - Evgeni M Glebov
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str, 630090, Novosibirsk, Russian Federation.
- Novosibirsk State University, 2 Pirogova Str., 630090, Novosibirsk, Russian Federation.
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Nathanael JG, Yuan B, Wille U. Oxidative Damage of Aliphatic Amino Acid Residues by the Environmental Pollutant NO 3·: Impact of Water on the Reactivity. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:7687-7695. [PMID: 35671332 DOI: 10.1021/acs.est.2c00863] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The rate of oxidative damage of aliphatic amino acids and dipeptides by the environmental pollutant nitrate radical (NO3·) in an aqueous acidic environment was studied by laser flash photolysis. The reactivity dropped by a factor of about four for amino acid residues with secondary amide bonds and by a factor of up to nearly 20 for amino acid residues with tertiary amide bonds, compared with that in acetonitrile. According to density functional theory studies, the lower reactivity is due to protonation of the amide moiety, whereas in neutral water, hydrogen bonding with the amide should have little impact on the absolute reaction rate compared with that in acetonitrile. This finding can be rationalized by the high reactivity and broad reaction pattern of NO3·. Although hydrogen bonding involving the amide group raises the energies associated with some electron transfer processes, alternative low-energy pathways remain available so that the overall reaction rate is barely affected. The undiminished high reactivity of NO3· toward aliphatic amino acid residues in a neutral aqueous environment highlights the health-damaging potential of exposure to the combined air pollutants nitrogen dioxide (NO2·) and ozone (O3).
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Affiliation(s)
- Joses Grady Nathanael
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Bing Yuan
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Uta Wille
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
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Paradzinsky M, Troya D, Tanko JM. Insight into Hydrogen Abstractions by Nitrate Radical: Structural, Solvent Effects, and Evidence for a Polar Transition State. J Phys Chem A 2021; 125:5471-5480. [PMID: 34157229 DOI: 10.1021/acs.jpca.1c01726] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of a polarized transition state and solvent effects on nitrate radical reactions was examined with a previously under-reported class of substrates, ethers, for their atmospheric implications. Absolute rate constants for hydrogen abstraction from a series of alcohols, ethers, and alkanes by nitrate radical have been measured in acetonitrile, water, and mixtures of these two solvents. Across all of these classes of compounds, using a modified form of the Evans-Polanyi relationship, it is demonstrated that the observed structure/reactivity trends can be reconciled by considering the number of abstractable hydrogens, strength of the C-H bond, and ionization potential (IP) of the substrate. Hydrogen abstractions by nitrate radical occur with low selectivity and are characterized by an early transition state (α ≈ 0.3). The dependence of the rate constant on IP suggests a polar transition state with some degree (<10%) of charge transfer. These conclusions stand for reactions conducted in solution (CH3CN and H2O) as well as gas-phase values. Because of this polar transition state, the rate constants increase going from the gas phase to a polar solvent, and the magnitude of the increase is consistent with Kirkwood theory.
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Affiliation(s)
- Mark Paradzinsky
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Diego Troya
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - James M Tanko
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
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Cui J, Nathanael JG, Wille U. Oxidative Damage of S‐Containing Amino Acids by the Environmental Radical NO
3
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: A Kinetic, Product and Computational Study. ChemistrySelect 2021. [DOI: 10.1002/slct.202101027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Jiaxing Cui
- School of Chemistry Bio21 Institute The University of Melbourne 30 Flemington Road Parkville Victoria 3010 Australia
| | - Joses G. Nathanael
- School of Chemistry Bio21 Institute The University of Melbourne 30 Flemington Road Parkville Victoria 3010 Australia
| | - Uta Wille
- School of Chemistry Bio21 Institute The University of Melbourne 30 Flemington Road Parkville Victoria 3010 Australia
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Nathanael JG, White JM, Richter A, Nuske MR, Wille U. Oxidative damage of proline residues by nitrate radicals (NO 3˙): a kinetic and product study. Org Biomol Chem 2020; 18:6949-6957. [PMID: 32936182 DOI: 10.1039/d0ob01337d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tertiary amides, such as in N-acylated proline or N-methyl glycine residues, react rapidly with nitrate radicals (NO3˙) with absolute rate coefficients in the range of 4-7 × 108 M-1 s-1 in acetonitrile. The major pathway proceeds through oxidative electron transfer (ET) at nitrogen, whereas hydrogen abstraction is only a minor contributor under these conditions. However, steric hindrance at the amide, for example by alkyl side chains at the α-carbon, lowers the rate coefficient by up to 75%, indicating that NO3˙-induced oxidation of amide bonds proceeds through initial formation of a charge transfer complex. Furthermore, the rate of oxidative damage of proline and N-methyl glycine is significantly influenced by its position in a peptide. Thus, neighbouring peptide bonds, particularly in the N-direction, reduce the electron density at the tertiary amide, which slows down the rate of ET by up to one order of magnitude. The results from these model studies suggest that the susceptibility of proline residues in peptides to radical-induced oxidative damage should be considerably reduced, compared with the single amino acid.
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Affiliation(s)
- Joses G Nathanael
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia.
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Oxidative Repair of Pyrimidine Cyclobutane Dimers by Nitrate Radicals (NO3•): A Kinetic and Computational Study. CHEMISTRY 2020. [DOI: 10.3390/chemistry2020027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Pyrimidine cyclobutane dimers are hazardous DNA lesions formed upon exposure of DNA to UV light, which can be repaired through oxidative electron transfer (ET). Laser flash photolysis and computational studies were performed to explore the role of configuration and constitution at the cyclobutane ring on the oxidative repair process, using the nitrate radical (NO3•) as oxidant. The rate coefficients of 8–280 × 107 M−1 s−1 in acetonitrile revealed a very high reactivity of the cyclobutane dimers of N,N’-dimethylated uracil (DMU), thymine (DMT), and 6-methyluracil (DMU6-Me) towards NO3•, which likely proceeds via ET at N(1) as a major pathway. The overall rate of NO3• consumption was determined by (i) the redox potential, which was lower for the syn- than for the anti-configured dimers, and (ii) the accessibility of the reaction site for NO3•. In the trans dimers, both N(1) atoms could be approached from above and below the molecular plane, whereas in the cis dimers, only the convex side was readily accessible for NO3•. The higher reactivity of the DMT dimers compared with isomeric DMU dimers was due to the electron-donating methyl groups on the cyclobutane ring, which increased their susceptibility to oxidation. On the other hand, the approach of NO3• to the dimers of DMU6-Me was hindered by the methyl substituents adjacent to N(1), making these dimers the least reactive in this series.
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Nathanael JG, Wille U. Oxidative Damage in Aliphatic Amino Acids and Di- and Tripeptides by the Environmental Free Radical Oxidant NO 3•: The Role of the Amide Bond Revealed by Kinetic and Computational Studies. J Org Chem 2019; 84:3405-3418. [PMID: 30742433 DOI: 10.1021/acs.joc.8b03224] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Kinetic and computational data reveal a complex behavior of the important environmental free radical oxidant NO3• in its reactions with aliphatic amino acids and di- and tripeptides, suggesting that attack at the amide N-H bond in the peptide backbone is a highly viable pathway, which proceeds through a proton-coupled electron transfer (PCET) mechanism with a rate coefficient of about 1 × 106 M-1 s-1 in acetonitrile. Similar rate coefficients were determined for hydrogen abstraction from the α-carbon and from tertiary C-H bonds in the side chain. The obtained rate coefficients for the reaction of NO3• with aliphatic di- and tripeptides suggest that attack occurs at all of these sites in each individual amino acid residue, which makes aliphatic peptide sequences highly vulnerable to NO3•-induced oxidative damage. No evidence for amide neighboring group effects, which have previously been found to facilitate radical-induced side-chain damage in phenylalanine, was found for the reaction of NO3• with side chains in aliphatic peptides.
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Affiliation(s)
- Joses G Nathanael
- School of Chemistry, Bio21 Institute , The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
| | - Uta Wille
- School of Chemistry, Bio21 Institute , The University of Melbourne , 30 Flemington Road , Parkville , Victoria 3010 , Australia
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Stevens AL, Novakovic S, White JM, Wong WWH, Smith TA, Ghiggino KP, Paige MF, Steer RP. Exciton Dynamics of Photoexcited Pendant Porphyrin Polymers in Solution and in Thin Films. J Phys Chem A 2018; 122:9605-9614. [DOI: 10.1021/acs.jpca.8b09321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Amy L. Stevens
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada S7N5C9
| | | | | | | | | | | | - Matthew F. Paige
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada S7N5C9
| | - Ronald P. Steer
- Department of Chemistry, University of Saskatchewan, Saskatoon, SK, Canada S7N5C9
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Nathanael JG, Gamon LF, Cordes M, Rablen PR, Bally T, Fromm KM, Giese B, Wille U. Amide Neighbouring-Group Effects in Peptides: Phenylalanine as Relay Amino Acid in Long-Distance Electron Transfer. Chembiochem 2018; 19:922-926. [PMID: 29460322 DOI: 10.1002/cbic.201800098] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Indexed: 12/27/2022]
Abstract
In nature, proteins serve as media for long-distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single-step superexchange or through a multi-step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long-distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilise the Phe radical cation. This neighbouring-amide-group effect helps improve understanding of the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration.
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Affiliation(s)
- Joses G Nathanael
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria, 3010, Australia
| | - Luke F Gamon
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria, 3010, Australia
| | - Meike Cordes
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Paul R Rablen
- Department of Chemistry and Biochemistry, Swarthmore College, 500 College Avenue, Swarthmore, PA, 19081-1397, USA
| | - Thomas Bally
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700, Fribourg, Switzerland
| | - Katharina M Fromm
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700, Fribourg, Switzerland
| | - Bernd Giese
- Department of Chemistry, University of Fribourg, Chemin du Musée 9, 1700, Fribourg, Switzerland
| | - Uta Wille
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria, 3010, Australia
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Gamon LF, Wille U. Oxidative Damage of Biomolecules by the Environmental Pollutants NO 2• and NO 3•. Acc Chem Res 2016; 49:2136-2145. [PMID: 27668965 DOI: 10.1021/acs.accounts.6b00219] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Air pollution is responsible for the premature death of about 7 million people every year. Ozone (O3) and nitrogen dioxide (NO2•) are the key gaseous pollutants in the troposphere, which predominantly result from combustion processes. Their inhalation leads to reactions with constituents in the airway surface fluids (ASF) of the respiratory tract and/or lungs. ASF contain small molecular-weight antioxidants, which protect the underlying epithelial cells against oxidative damage. When this defense system is overwhelmed, proteins and lipids present on cell surfaces or within the ASF become vulnerable to attack. The resulting highly reactive protein and lipid oxidation products could subsequently damage the epithelial cells through secondary reactions, thereby causing inflammation. While reactions of NO2• with biological molecules are considered to proceed through radical pathways, the biological effect of O3 is attributed to its high reactivity with π systems. Because O3 and NO2• always coexist in the polluted ambient atmosphere, synergistic effects resulting from in situ formed strongly oxidizing nitrate radicals (NO3•) may also require consideration. For example, in vitro product studies revealed that phenylalanine, which is inert not only to oxidants produced through biochemical processes, but also to NO2• or O3 in isolation, is damaged by NO3•. The reaction is initiated by oxidation of the aromatic ring and, depending on the availability of NO2•, leads to formation of nitrophenylalanine or β-nitrooxyphenylalanine, which could serve as marker for NO3•-induced oxidative damage in peptides. More easily oxidizable aromatic amino acids are directly attacked by NO2• and are converted to the same products independent of whether O3 is also present. Remarkably, NO2•-induced oxidative damage in peptides occurs not only through the well-established radical oxidation of peptide side chains, but also through an unprecedented fragmentation/rearrangement of the peptide backbone. This process is initiated by a nonradical N-nitrosation of a peptide bond involving the dimer of NO2•, i.e., N2O4, and contracts the peptide chain in the N → C direction by expelling one amino acid residue with simultaneous fusion of the remaining molecular termini, thereby forming a new peptide bond. This peptide cleavage could potentially be highly relevant for peptide segments with "nonvulnerable" side chains closer to the terminus that are not tied up in complex secondary and tertiary structures and therefore accessible for environmental oxidants. Likewise, NO2• reacts with cholesterol at the C═C moiety through an ionic mechanism, which leads to formation of 6-nitrocholesterol in the presence of moisture. Contrary to common belief, this clearly shows that ionic chemistry, in particular nitrosation reactions by intermediately formed NO+, requires consideration when assessing NO2• toxicity. This conclusion is supported by recent work by Colussi et al. (Enami, S.; Hoffmann, M. R.; Colussi, A. J. Absorption of inhaled NO2. J. Phys. Chem. B. 2009, 113, 7977-7981), who showed that anions in the airway surfaces fluids mediate NO2• absorption by catalyzing its hydrolytic disproportionation into NO2-/HNO2 and NO3-. These findings could be the key to our understanding why NO2•, despite its low water solubility, has such pronounced biological effects in vivo.
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Affiliation(s)
- Luke F. Gamon
- School of Chemistry and Bio21
Institute, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Uta Wille
- School of Chemistry and Bio21
Institute, The University of Melbourne, Parkville, VIC 3010, Australia
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