1
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Reyes Y, Adhikary A, Wnuk SF. Nitrogen-Centered Radicals Derived from Azidonucleosides. Molecules 2024; 29:2310. [PMID: 38792171 PMCID: PMC11124349 DOI: 10.3390/molecules29102310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 05/04/2024] [Accepted: 05/08/2024] [Indexed: 05/26/2024] Open
Abstract
Azido-modified nucleosides have been extensively explored as substrates for click chemistry and the metabolic labeling of DNA and RNA. These compounds are also of interest as precursors for further synthetic elaboration and as therapeutic agents. This review discusses the chemistry of azidonucleosides related to the generation of nitrogen-centered radicals (NCRs) from the azido groups that are selectively inserted into the nucleoside frame along with the subsequent chemistry and biological implications of NCRs. For instance, the critical role of the sulfinylimine radical generated during inhibition of ribonucleotide reductases by 2'-azido-2'-deoxy pyrimidine nucleotides as well as the NCRs generated from azidonucleosides by radiation-produced (prehydrated and aqueous) electrons are discussed. Regio and stereoselectivity of incorporation of an azido group ("radical arm") into the frame of nucleoside and selective generation of NCRs under reductive conditions, which often produce the same radical species that are observed upon ionization events due to radiation and/or other oxidative conditions that are emphasized. NCRs generated from nucleoside-modified precursors other than azidonucleosides are also discussed but only with the direct relation to the same/similar NCRs derived from azidonucleosides.
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Affiliation(s)
- Yahaira Reyes
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA;
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA;
| | - Stanislaw F. Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA;
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2
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Anderson RF, Shinde SS, Andrau L, Leung B, Skene C, White JM, Lobachevsky PN, Martin RF. Chemical Repair of Radical Damage to the GC Base Pair by DNA-Bound Bisbenzimidazoles. J Phys Chem B 2024. [PMID: 38686959 DOI: 10.1021/acs.jpcb.4c01069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The migration of an electron-loss center (hole) in calf thymus DNA to bisbenzimidazole ligands bound in the minor groove is followed by pulse radiolysis combined with time-resolved spectrophotometry. The initially observed absorption spectrum upon oxidation of DNA by the selenite radical is consistent with spin on cytosine (C), as the GC• pair neutral radical, followed by the spectra of oxidized ligands. The rate of oxidation of bound ligands increased with an increase in the ratio (r) ligands per base pair from 0.005 to 0.04. Both the rate of ligand oxidation and the estimated range of hole transfer (up to 30 DNA base pairs) decrease with the decrease in one-electron reduction potential between the GC• pair neutral radical of ca. 1.54 V and that of the ligand radicals (E0', 0.90-0.99 V). Linear plots of log of the rate of hole transfer versus r give a common intercept at r = 0 and a free energy change of 12.2 ± 0.3 kcal mol-1, ascribed to the GC• pair neutral radical undergoing a structural change, which is in competition to the observed hole transfer along DNA. The rate of hole transfer to the ligands at distance, R, from the GC• pair radical, k2, is described by the relationship k2 = k0 exp(constant/R), where k0 includes the rate constant for surmounting a small barrier.
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Affiliation(s)
- Robert F Anderson
- School of Chemical Sciences, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand
| | - Sujata S Shinde
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand
| | - Laura Andrau
- School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne 3052, Australia
| | - Brenda Leung
- School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne 3052, Australia
| | - Colin Skene
- School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne 3052, Australia
| | - Jonathan M White
- School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne 3052, Australia
| | - Pavel N Lobachevsky
- Molecular Radiation Biology, Peter MacCallum Cancer Centre, Melbourne 3052, Australia
| | - Roger F Martin
- School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne 3052, Australia
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3
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Peng H, Vu S, Retes P, Ward S, Kumar A, Sevilla MD, Adhikary A, Greenberg MM. Photochemical and Single Electron Transfer Generation of 2'-Deoxycytidin- N4-yl Radical from Oxime Esters. J Org Chem 2023; 88:7381-7390. [PMID: 37220149 PMCID: PMC10308854 DOI: 10.1021/acs.joc.3c00646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A 2'-deoxycytidin-N4-yl radical (dC·), a strong oxidant that also abstracts hydrogen atoms from carbon-hydrogen bonds, is produced in a variety of DNA damaging processes. We describe here the independent generation of dC· from oxime esters under UV-irradiation or single electron transfer conditions. Support for this σ-type iminyl radical generation is provided by product studies carried out under aerobic and anaerobic conditions, as well as electron spin resonance (ESR) characterization of dC· in a homogeneous glassy solution at low temperature. Density functional theory (DFT) calculations also support fragmentation of the corresponding radical anions of oxime esters 2d and 2e to dC· and subsequent hydrogen atom abstraction from organic solvents. The corresponding 2'-deoxynucleotide triphosphate (dNTP) of isopropyl oxime ester 2c (5) is incorporated opposite 2'-deoxyadenosine and 2'-deoxyguanosine by a DNA polymerase with approximately equal efficiency. Photolysis experiments of DNA containing 2c support dC· generation and indicate that the radical produces tandem lesions when flanked on the 5'-side by 5'-d(GGT). These experiments suggest that oxime esters are reliable sources of nitrogen radicals in nucleic acids that will be useful mechanistic tools and possibly radiosensitizing agents when incorporated in DNA.
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Affiliation(s)
- Haihui Peng
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, United States
| | - Son Vu
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, United States
| | - Parker Retes
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Samuel Ward
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Anil Kumar
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Michael D Sevilla
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, United States
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4
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Kumar A, Sevilla MD. Proton-Transfer Reactions in One-Electron-Oxidized G-Quadruplexes: A Density Functional Theory Study. J Phys Chem B 2022; 126:1483-1491. [PMID: 35152699 PMCID: PMC8881324 DOI: 10.1021/acs.jpcb.1c10529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recently, G-quadruplexes (Gq) formed in B-DNA as secondary structures are found to be important therapeutic targets and material for developing nanodevices. Gq are guanine-rich and thus susceptible to oxidative damage by producing short-lived intermediate radicals via proton-transfer reactions. Understanding the mechanisms of radical formation in Gq is of fundamental interest to understand the early stages of DNA damage. Herein, we used density functional theory including aqueous phase (ωB97XD-PCM/6-31++G**) and considered single layer of Gq [G-quartets (G4): association of four guanines in a cyclic Hoogsteen hydrogen-bonded arrangement (Scheme 1)] to unravel the mechanisms of formation of intermediates by calculating the relative Gibbs free energies and spin density distributions of one-electron-oxidized G4 and its various proton-transfer states: G•+, G(N1-H)•, G(N2-H')•, G(N2-H″)•, G(N1-H)•-(H+O6)G, and G(N2-H)•-(H+N7)G. The present calculation predicts the formation of G(N2-H)•-(H+N7)G, which is only ca. 0.8 kcal/mol higher in energy than the initially formed G•+. The formation of G(N2-H)•-(H+N7)G plays a key role in explaining the formation of 8-OG along with G(N1-H)• formation via tautomerization from G(N2-H)•, as proposed recently.
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Affiliation(s)
- Anil Kumar
- Corresponding Author: . Tel: +1 248 370 2327, . Tel: +1 248 370 2328
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5
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Peng H, Jie J, Mortimer IP, Ma Z, Su H, Greenberg MM. Reactivity and DNA Damage by Independently Generated 2'-Deoxycytidin- N4-yl Radical. J Am Chem Soc 2021; 143:14738-14747. [PMID: 34467764 DOI: 10.1021/jacs.1c06425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Oxidative stress produces a variety of radicals in DNA, including pyrimidine nucleobase radicals. The nitrogen-centered DNA radical 2'-deoxycytidin-N4-yl radical (dC·) plays a role in DNA damage mediated by one electron oxidants, such as HOCl and ionizing radiation. However, the reactivity of dC· is not well understood. To reduce this knowledge gap, we photochemically generated dC· from a nitrophenyl oxime nucleoside and within chemically synthesized oligonucleotides from the same precursor. dC· formation is confirmed by transient UV-absorption spectroscopy in laser flash photolysis (LFP) experiments. LFP and duplex DNA cleavage experiments indicate that dC· oxidizes dG. Transient formation of the dG radical cation (dG+•) is observed in LFP experiments. Oxidation of the opposing dG in DNA results in hole transfer when the opposing dG is part of a dGGG sequence. The sequence dependence is attributed to a competition between rapid proton transfer from dG+• to the opposing dC anion formed and hole transfer. Enhanced hole transfer when less acidic O6-methyl-2'-deoxyguanosine is opposite dC· supports this proposal. dC· produces tandem lesions in sequences containing thymidine at the 5'-position by abstracting a hydrogen atom from the thymine methyl group. The corresponding thymidine peroxyl radical completes tandem lesion formation by reacting with the 5'-adjacent nucleotide. As dC· is reduced to dC, its role in the process is traceless and is only detectable because of the ability to independently generate it from a stable precursor. These experiments reveal that dC· oxidizes neighboring nucleotides, resulting in deleterious tandem lesions and hole transfer in appropriate sequences.
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Affiliation(s)
- Haihui Peng
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ifor P Mortimer
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Zehan Ma
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
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6
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Mudgal M, Dang TP, Sobczak AJ, Lumpuy DA, Dutta P, Ward S, Ward K, Alahmadi M, Kumar A, Sevilla MD, Wnuk SF, Adhikary A. Site of Azido Substitution in the Sugar Moiety of Azidopyrimidine Nucleosides Influences the Reactivity of Aminyl Radicals Formed by Dissociative Electron Attachment. J Phys Chem B 2020; 124:11357-11370. [PMID: 33270461 DOI: 10.1021/acs.jpcb.0c08201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this work, electron-induced site-specific formation of neutral π-type aminyl radicals (RNH·) and their reactions with pyrimidine nucleoside analogs azidolabeled at various positions in the sugar moiety, e.g., at 2'-, 3'-, 4'-, and 5'- sites along with a model compound 3-azido-1-propanol (3AZPrOH), were investigated. Electron paramagnetic resonance (EPR) studies confirmed the site and mechanism of RNH· formation via dissociative electron attachment-mediated loss of N2 and subsequent facile protonation from the solvent employing the 15N-labeled azido group, deuterations at specific sites in the sugar and base, and changing the solvent from H2O to D2O. Reactions of RNH· were investigated employing EPR by warming these samples from 77 K to ca. 170 K. RNH· at a primary carbon site (5'-azido-2',5'-dideoxyuridine, 3AZPrOH) facilely converted to a σ-type iminyl radical (R═N·) via a bimolecular H-atom abstraction forming an α-azidoalkyl radical. RNH· when at a secondary carbon site (e.g., 2'-azido-2'-deoxyuridine) underwent bimolecular electrophilic addition to the C5═C6 double bond of a proximate pyrimidine base. Finally, RNH· at tertiary alkyl carbon (4'-azidocytidine) underwent little reaction. These results show the influence of the stereochemical and electronic environment on RNH· reactivity and allow the selection of those azidonucleosides that would be most effective in augmenting cellular radiation damage.
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Affiliation(s)
- Mukesh Mudgal
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Thao P Dang
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Adam J Sobczak
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Daniel A Lumpuy
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Priya Dutta
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Samuel Ward
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Katherine Ward
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Moaadh Alahmadi
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Anil Kumar
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Michael D Sevilla
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Stanislaw F Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
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7
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Hatanaka M, Liu Y, Miyasaka M. A 1-Phenylbiguanide-iodine Complex — An Imino π–Cation Radical of Guanidines —. CHEM LETT 2020. [DOI: 10.1246/cl.200251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Masashi Hatanaka
- Division of Materials Science and Engineering, Graduate School of Engineering, Tokyo Denki University, 5 Senju-Asahi-cho, Adachi-ku, Tokyo 101-8307, Japan
| | - Yiming Liu
- Division of Materials Science and Engineering, Graduate School of Engineering, Tokyo Denki University, 5 Senju-Asahi-cho, Adachi-ku, Tokyo 101-8307, Japan
| | - Makoto Miyasaka
- Division of Materials Science and Engineering, Graduate School of Engineering, Tokyo Denki University, 5 Senju-Asahi-cho, Adachi-ku, Tokyo 101-8307, Japan
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8
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A computational investigation of cytosine and 5-methyl cytosine reactivity by means of ionization potentials and one specific methylation pathway. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Anderson RF, Shinde SS, Maroz A, Reynisson J. The reduction potential of the slipped GC base pair in one-electron oxidized duplex DNA. Phys Chem Chem Phys 2020; 22:642-646. [PMID: 31822872 DOI: 10.1039/c9cp05544d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Redox equilibrium between the low potential aniline radical cation and the guanine in the GC base pair of duplex DNA has been established using pulse radiolysis. We relate the measurement of a radical one-electron reduction potential, E0', of 1.01 ± 0.03 V to the perturbation of the GC base pair to accommodate the neutral guanyl radical in an energetically more stable 'slipped' structure. The formation of the 'slipped' structure is exothermic by -11.4 kcal mol-1 as calculated by DFT, which is inline with our experimental results.
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Affiliation(s)
- Robert F Anderson
- Auckland Cancer Society Research Centre, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand.
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10
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Kumar A, Becker D, Adhikary A, Sevilla MD. Reaction of Electrons with DNA: Radiation Damage to Radiosensitization. Int J Mol Sci 2019; 20:E3998. [PMID: 31426385 PMCID: PMC6720166 DOI: 10.3390/ijms20163998] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 08/01/2019] [Accepted: 08/12/2019] [Indexed: 01/19/2023] Open
Abstract
This review article provides a concise overview of electron involvement in DNA radiation damage. The review begins with the various states of radiation-produced electrons: Secondary electrons (SE), low energy electrons (LEE), electrons at near zero kinetic energy in water (quasi-free electrons, (e-qf)) electrons in the process of solvation in water (presolvated electrons, e-pre), and fully solvated electrons (e-aq). A current summary of the structure of e-aq, and its reactions with DNA-model systems is presented. Theoretical works on reduction potentials of DNA-bases were found to be in agreement with experiments. This review points out the proposed role of LEE-induced frank DNA-strand breaks in ion-beam irradiated DNA. The final section presents radiation-produced electron-mediated site-specific formation of oxidative neutral aminyl radicals from azidonucleosides and the evidence of radiosensitization provided by these aminyl radicals in azidonucleoside-incorporated breast cancer cells.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA
| | - David Becker
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA
| | - Michael D Sevilla
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA.
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11
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Kumar A, Sevilla MD. Excited States of One-Electron Oxidized Guanine-Cytosine Base Pair Radicals: A Time Dependent Density Functional Theory Study. J Phys Chem A 2019; 123:3098-3108. [PMID: 30896952 DOI: 10.1021/acs.jpca.9b00906] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
One-electron oxidized guanine (G•+) in DNA generates several short-lived intermediate radicals via proton transfer reactions resulting in the formation of neutral guanine radicals. The identification of these radicals in DNA is of fundamental interest to understand the early stages of DNA damage. Herein, we used time-dependent density functional theory (TD-ωB97XD-PCM/6-31G(3df,p)) to calculate the vertical excitation energies of one-electron oxidized G and G-cytosine (C) base pair in various protonation states: G•+, G(N1-H)•, and G(N2-H)•, as well as G•+-C, G(N1-H)•-(H+)C, G(N1-H)•-(N4-H+)C), G(N1-H)•-C, and G(N2-H)•-C in aqueous phase. The calculated UV-vis spectra of these radicals are in good agreement with the experiment for the G radical species when the calculated values are red-shifted by 40-70 nm. The present calculations show that the lowest energy transitions of proton transfer species (G(N1-H)•-(H+)C, G(N1-H)•-(N4-H+)C, and G(N1-H)•-C) are substantially red-shifted in comparison to the spectrum of G•+-C. The calculated spectrum of G(N2-H)•-C shows intense absorption (high oscillator strength), which matches the strong absorption in the experimental spectra of G(N2-H)• at 600 nm. The present calculations predict the lowest charge transfer transition of C → G•+ is π → π* in nature and lies in the UV region (3.4-4.3 eV) with small oscillator strength.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry , Oakland University , Rochester , Michigan 48309 , United States
| | - Michael D Sevilla
- Department of Chemistry , Oakland University , Rochester , Michigan 48309 , United States
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12
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Wang Y, Zhao H, Yang C, Jie J, Dai X, Zhou Q, Liu K, Song D, Su H. Degradation of Cytosine Radical Cations in 2′-Deoxycytidine and in i-Motif DNA: Hydrogen-Bonding Guided Pathways. J Am Chem Soc 2019; 141:1970-1979. [DOI: 10.1021/jacs.8b10743] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Yinghui Wang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
- University of Chinese Academy of Science, Beijing 100049, P. R. China
| | - Hongmei Zhao
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
| | - Chunfan Yang
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Jialong Jie
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Xiaojuan Dai
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Qian Zhou
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Kunhui Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Di Song
- Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, P. R. China
| | - Hongmei Su
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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13
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Wen Z, Peng J, Tuttle PR, Ren Y, Garcia C, Debnath D, Rishi S, Hanson C, Ward S, Kumar A, Liu Y, Zhao W, Glazer PM, Liu Y, Sevilla MD, Adhikary A, Wnuk SF. Electron-Mediated Aminyl and Iminyl Radicals from C5 Azido-Modified Pyrimidine Nucleosides Augment Radiation Damage to Cancer Cells. Org Lett 2018; 20:7400-7404. [PMID: 30457873 PMCID: PMC6465127 DOI: 10.1021/acs.orglett.8b03035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Two classes of azido-modified pyrimidine nucleosides were synthesized as potential radiosensitizers; one class is 5-azidomethyl-2'-deoxyuridine (AmdU) and cytidine (AmdC), while the second class is 5-(1-azidovinyl)-2'-deoxyuridine (AvdU) and cytidine (AvdC). The addition of radiation-produced electrons to C5-azido nucleosides leads to the formation of π-aminyl radicals followed by facile conversion to σ-iminyl radicals either via a bimolecular reaction involving intermediate α-azidoalkyl radicals in AmdU/AmdC or by tautomerization in AvdU/AvdC. AmdU demonstrates effective radiosensitization in EMT6 tumor cells.
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Affiliation(s)
- Zhiwei Wen
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Jufang Peng
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Paloma R. Tuttle
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Yaou Ren
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Carol Garcia
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Dipra Debnath
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Sunny Rishi
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Cameron Hanson
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Samuel Ward
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Yanfeng Liu
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Weixi Zhao
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Peter M. Glazer
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, United States
| | - Yuan Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Michael D. Sevilla
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, United States
| | - Stanislaw F. Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
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14
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Cadet J, Wagner JR, Angelov D. Biphotonic Ionization of DNA: From Model Studies to Cell. Photochem Photobiol 2018; 95:59-72. [PMID: 30380156 DOI: 10.1111/php.13042] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 10/16/2018] [Indexed: 12/13/2022]
Abstract
Oxidation reactions triggered by low-intensity UV photons represent a minor contribution with respect to the overwhelming pyrimidine base dimerization in both isolated and cellular DNA. The situation is totally different when DNA is exposed to high-intensity UVC radiation under conditions where biphotonic ionization of the four main purine and pyrimidine bases becomes predominant at the expense of singlet excitation processes. The present review article provides a critical survey of the main chemical reactions of the base radical cations thus generated by one-electron oxidation of nucleic acids in model systems and cells. These include oxidation of the bases with the predominant formation of 8-oxo-7,8-dihydroguanine as the result of preferential hole transfer to guanine bases that act as sinks in isolated and cellular DNA. In addition to hydration, other nucleophilic addition reactions involving the guanine radical cation give rise to intra- and interstrand cross-links together with DNA-protein cross-links. Information is provided on the utilization of high-intensity UV laser pulses as molecular biology tools for studying DNA conformational features, nucleic acid-protein interactions and nucleic acid reactivity through DNA-protein cross-links and DNA footprinting experiments.
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Affiliation(s)
- Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - J Richard Wagner
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Dimitar Angelov
- Laboratoire de Biologie et Modélisation de la Cellule LBMC, CNRS-UMR 5239, Université de Lyon, École Normale Supérieure de Lyon, Lyon, France
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15
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Abstract
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Conventionally, the
singly occupied molecular orbital (SOMO) of
a radical species is considered to be the highest occupied molecular
orbital (HOMO), but this is not the case always. In this study, we
considered a number of radicals from smallest diatomic anion radicals
such as superoxide anion radical to one-electron oxidized DNA related
base radicals that show the SOMO is energetically lower than one or
more doubly occupied molecular orbitals (MOs) (SOMO–HOMO level
inversion). The electronic configurations are calculated employing
the B3LYP/6-31++G** method, with the inclusion of aqueous phase via
the integral equation formalism of the polarized continuum model solvation
model. From the extensive study of the electronic configurations of
radicals produced by one-electron oxidation or reduction of natural-DNA
bases, bromine-, sulfur-, selenium-, and aza-substituted DNA bases,
as well as 20 diatomic molecules, we highlight the following important
findings: (i) SOMO–HOMO level inversion is a common phenomenon
in radical species. (ii) The more localized spin density in σ-orbital
on a single atom (carbon, nitrogen, oxygen, sulfur, or selenium),
the greater the gap between HOMO and SOMO. (iii) In species with SOMO–HOMO
level inversion, one-electron oxidation takes place from HOMO not
from the SOMO, which produces a molecule in its triplet ground state.
Oxidation of aqueous superoxide anion producing triplet molecular
oxygen is one example of many. (iv) These results are for conventional
radicals and in contrast with those reported for distonic radical
anions in which SOMO–HOMO gaps are smaller for more localized
radicals and the orbital inversions vanish in water. Our findings
yield new insights into the properties of free radical systems.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Michael D Sevilla
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
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16
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Barkam S, Ortiz J, Saraf S, Eliason N, Mccormack R, Das S, Gupta A, Neal C, Petrovici A, Hanson C, Sevilla MD, Adhikary A, Seal S. Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:20039-20050. [PMID: 28936278 PMCID: PMC5602578 DOI: 10.1021/acs.jpcc.7b05725] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•2- from reduction of NO3- in CNPs synthesized from Ce(III) nitrate). Physicochemical properties of these CNPs, e.g., dispersion stability, hydrodynamic size, signature surface chemistry, SOD-mimetic activity, and oxidation potentials were found to be significantly affected by the anions of the precursor salts. CNPs synthesized from Ce(III) nitrate and Ce(III) chloride exhibited higher extent of SOD-mimetic activities. Therefore, these CNPs were studied extensively employing in-situ UV-Visible spectroelectrochemistry and changing the counterion concentrations affected the oxidation potentials of these CNPs. Thus, the physicochemical and antioxidant properties of CNPs can be modulated by anions of the precursor. Furthermore, our ESR studies present evidence of the formation of guanine cation radical (G•+) in 5'-dGMP via UV-photoionization at 77 K in the presence of CNPs synthesized from Ce(III) nitrate and chloride and CNPs act as the scavenger of radiation-produced electrons.
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Affiliation(s)
- Swetha Barkam
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Julian Ortiz
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Shashank Saraf
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Nicholas Eliason
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Rameech Mccormack
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Soumen Das
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
- NanoScience Technology Center (NSTC), Materials Science Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Ankur Gupta
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Craig Neal
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
| | - Alex Petrovici
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, MI – 48309, USA
| | - Cameron Hanson
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, MI – 48309, USA
| | - Michael D. Sevilla
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, MI – 48309, USA
| | - Amitava Adhikary
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, MI – 48309, USA
- Corresponding authors: Prof. Amitava Adhikary, , Telephone: 248-370-2094, Fax: 248-370-2321; Prof. Sudipta Seal, , Telephone: 407-823-5277 or 407-882-1458, Fax: 407-882-1156 or 407-823-0208
| | - Sudipta Seal
- Advanced Materials Processing and Analysis Center (AMPAC), Materials Science and Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
- NanoScience Technology Center (NSTC), Materials Science Engineering (MSE), University of Central Florida, 4000, Central Florida Boulevard, Orlando, Fl – 32816, USA
- College of Medicine, University of Central Florida, 6850 Lake Nona Blvd, Orlando, FL – 32827, USA
- Corresponding authors: Prof. Amitava Adhikary, , Telephone: 248-370-2094, Fax: 248-370-2321; Prof. Sudipta Seal, , Telephone: 407-823-5277 or 407-882-1458, Fax: 407-882-1156 or 407-823-0208
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17
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Kumar A, Sevilla MD. Cytosine Iminyl Radical (cytN •) Formation via Electron-Induced Debromination of 5-Bromocytosine: A DFT and Gaussian 4 Study. J Phys Chem A 2017; 121:4825-4829. [PMID: 28586202 PMCID: PMC5521985 DOI: 10.1021/acs.jpca.7b04034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Halogen-substituted pyrimidines, such as 5-bromouracil and 5-iodouracil, have been used as radio therapeutic (RT) agents in cancer treatment. The radiosensitizing activity of 5-bromouracil is attributed to its reaction with electron which produce the highly reactive uracil-5-yl radical by dissociating the C5-Br bond. Using density functional methods and highly accurate Gaussian 4 (G4) theory, herein, we show that 5-bromocytosine (5-Brcyt) after reaction with electron, also, leads to the formation of cytosine-5-yl radical. However, our results show that this species can subsequently undergo a base-catalyzed tautomerization reaction to form the π-aminyl radical followed by a second tautomerization to the thermodynamically most stable σ-iminyl radical (cytN•). From the present theoretical calculations, we infer that the mechanism of the formation of cytN• by one-electron reduction of 5-Brcyt is straightforward and may take place in 5-Brcyt-labeled DNA in competition with the usual reactions expected for the cytosine-5-yl radical such as abstraction and water addition.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309
| | - M. D. Sevilla
- Department of Chemistry, Oakland University, Rochester, Michigan 48309
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18
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Mudgal M, Rishi S, Lumpuy DA, Curran KA, Verley KL, Sobczak AJ, Dang TP, Sulimoff N, Kumar A, Sevilla MD, Wnuk SF, Adhikary A. Prehydrated One-Electron Attachment to Azido-Modified Pentofuranoses: Aminyl Radical Formation, Rapid H-Atom Transfer, and Subsequent Ring Opening. J Phys Chem B 2017; 121:4968-4980. [PMID: 28425714 DOI: 10.1021/acs.jpcb.7b01838] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Methyl 2-azido-2-deoxy-α-d-lyxofuranoside (1a) and methyl 2-azido-2-deoxy-β-d-ribofuranoside (2) were prepared from d-xylose or d-arabinose, respectively. Employing ESR and DFT/B3LYP/6-31G* calculations, we investigated (i) aminyl radical (RNH·) formation and (ii) reaction pathways of RNH·. Prehydrated electron attachment to 1a and 2 at 77 K produced transient azide anion radical (RN3·-) which reacts via rapid N2 loss at 77 K, forming nitrene anion radical (RN·-). Rapid protonation of RN·- at 77 K formed RNH· and -OH. 15N-labeled-1a confirmed this mechanism. Investigations employing in-house synthesized site-specifically deuterated derivatives of 1a (e.g., CH3 (1b), C4 (1c), and C5 (1d)) established that (a) a facile intramolecular H atom transfer from C5 to RNH· generated C5· and RNH2. C5· formation had a small deuterium kinetic isotope effect suggesting that this reaction does not occur via direct H atom abstraction. (b) Subsequently, C5· underwent a facile unimolecular conversion to ring-opened C4·. Identification of ring-opened C4· intermediate confirms the mechanism of C5'· mediated unaltered base release associated with DNA-strand break. However, for 2, ESR studies established thermally activated intermolecular H atom abstraction by RNH· from the methyl group at C1. Thus, sugar ring configuration strongly influences the site and pathway of RNH· mediated reactions in pentofuranoses.
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Affiliation(s)
- Mukesh Mudgal
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Sunny Rishi
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Daniel A Lumpuy
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Keaton A Curran
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Kathryn Lynn Verley
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Adam J Sobczak
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Thao P Dang
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Natasha Sulimoff
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Anil Kumar
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Michael D Sevilla
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
| | - Stanislaw F Wnuk
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
| | - Amitava Adhikary
- Department of Chemistry, Oakland University , Rochester, Michigan 48309, United States
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19
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Effects of ionization on stability of 1-methylcytosine - DFT and PCM studies. J Mol Model 2016; 22:146. [PMID: 27259531 PMCID: PMC4893064 DOI: 10.1007/s00894-016-3020-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/26/2016] [Indexed: 01/01/2023]
Abstract
Consequences of ionization were studied by quantum-chemical methods (DFT and PCM) for 1-methylcytosine (MC)—a model of the nucleobase cytosine (C) connected with sugar in DNA. For calculations, three prototropic tautomers (one amino and two imino forms) and two imino zwitterions were considered, including conformational or configurational isomerism of exo heterogroups. Ionization and interactions between neighboring groups affect intramolecular proton-transfers, geometric and thermodynamic parameters, and electron delocalization for individual isomers. We discovered that an imino isomer is present in the isomeric mixture in the highest amount for positively ionized MC. Its contribution in neutral and negatively ionized MC is considerably smaller. Acid-base parameters for selected radical ions were estimated in the gas phase and compared to those of neutral MC. Gas-phase acidity of radical cations is close to that of the conjugate acid of MC, and gas-phase basicity of radical anions is close to that of the conjugate base of MC. Various routes of amino-imino conversion between neutral and ionized isomers were considered. Energetic-barrier for intramolecular proton-transfer in MC is close to that in the parent system—formamidine.
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20
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Sevilla MD, Becker D, Kumar A, Adhikary A. Gamma and Ion-Beam Irradiation of DNA: Free Radical Mechanisms, Electron Effects, and Radiation Chemical Track Structure. Radiat Phys Chem Oxf Engl 1993 2016; 128:60-74. [PMID: 27695205 DOI: 10.1016/j.radphyschem.2016.04.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The focus of our laboratory's investigation is to study the direct-type DNA damage mechanisms resulting from γ-ray and ion-beam radiation-induced free radical processes in DNA which lead to molecular damage important to cellular survival. This work compares the results of low LET (γ-) and high LET (ion-beam) radiation to develop a chemical track structure model for ion-beam radiation damage to DNA. Recent studies on protonation states of cytosine cation radicals in the N1-substituted cytosine derivatives in their ground state and 5-methylcytosine cation radicals in ground as well as in excited state are described. Our results exhibit a radical signature of excitations in 5-methylcytosine cation radical. Moreover, our recent theoretical studies elucidate the role of electron-induced reactions (low energy electrons (LEE), presolvated electrons (epre-), and aqueous (or, solvated) electrons (eaq-)). Finally DFT calculations of the ionization potentials of various sugar radicals show the relative reactivity of these species.
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Affiliation(s)
- Michael D Sevilla
- Department of Chemistry, Oakland University, Rochester, MI - 48309, USA
| | - David Becker
- Department of Chemistry, Oakland University, Rochester, MI - 48309, USA
| | - Anil Kumar
- Department of Chemistry, Oakland University, Rochester, MI - 48309, USA
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, Rochester, MI - 48309, USA
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21
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Shkrob IA, Marin TW. The AHA Moment: Assessment of the Redox Stability of Ionic Liquids Based on Aromatic Heterocyclic Anions (AHAs) for Nuclear Separations and Electric Energy Storage. J Phys Chem B 2015; 119:14766-79. [PMID: 26506410 DOI: 10.1021/acs.jpcb.5b09057] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Because of their extended conjugated bond network, aromatic compounds generally have higher redox stability than less saturated compounds. We conjectured that ionic liquids (ILs) consisting of aromatic heterocyclic anions (AHAs) may exhibit improved radiation and electrochemical stability. Such properties are important in applications of these ILs as diluents in radionuclide separations and electrolytes in the electric energy storage devices. In this study, we systematically examine the redox chemistry of the AHAs. Three classes of these anions have been studied: (i) simple 5-atom ring AHAs, such as the pyrazolide and triazolides, (ii) AHAs containing an adjacent benzene ring, and (iii) AHAs containing electron-withdrawing groups that were introduced to reduce their basicity and interaction with metal ions. It is shown that fragmentation in the reduced and oxidized states of these AHAs does not generally occur, and the two main products, respectively, are the H atom adduct and the imidyl radical. The latter species occurs either as an N σ-radical or as an N π-radical, depending on the length of the N-N bond, and the state that is stabilized in the solid matrix is frequently different from that having the lowest energy in the gas phase. In some instances, the formation of the sandwich π-stack dimer radical anions has been observed. For trifluoromethylated anions, H adduct formation did not occur; instead, there was facile loss of fluoride from their fluorinated groups. The latter can be problematic in nuclear separations, but beneficial in batteries. Overall, our study suggests that AHA-based ILs are viable candidates for use as radiation-exposed diluents and electrolytes.
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Affiliation(s)
- Ilya A Shkrob
- Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States
| | - Timothy W Marin
- Chemical Sciences and Engineering Division, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.,Chemistry Department, Benedictine University , 5700 College Road, Lisle, Illinois 60532, United States
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