1
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Storoniak P, Rak J, Wang H, Ko YJ, Bowen KH. Electrophilic Properties of 2'-Deoxyadenosine···Thymine Dimer: Photoelectron Spectroscopy and DFT Studies. J Phys Chem A 2021; 125:6591-6599. [PMID: 34310156 PMCID: PMC8389985 DOI: 10.1021/acs.jpca.1c03803] [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] [Indexed: 11/30/2022]
Abstract
The anion radical of the 2'-deoxyadenosine···thymine (dAT•-) pair has been investigated experimentally and theoretically in the gas phase. By employing negative-ion photoelectron spectroscopy (PES), we have registered a spectrum typical for the valence-bound anion, featuring a broad peak at the electron-binding energy (EBE) between ∼1.5 and 2.2 eV with the maximum at ∼1.9 eV. The measured value of the adiabatic electron affinity (AEA) for dAT was estimated to be ∼1.1 eV. Calculations performed at the M06-2X/6-31++G(d,p) level revealed that the structure, where thymine is coordinated to the sugar of dA by two hydrogen bonds, is responsible for the observed PES signal. The AEAG and the vertical detachment energy of 0.91 and 1.68 eV, respectively, calculated for this structure reproduce the experimental values well. The role of the possible proton transfer in the stabilization of anionic radical complexes is discussed.
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Affiliation(s)
- Piotr Storoniak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Janusz Rak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Haopeng Wang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Yeon Jae Ko
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kit H Bowen
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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2
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Abstract
Hydrogen bonds play a critical role in nucleobase studies as they encode genes, map protein structures, provide stability to the base pairs, and are involved in spontaneous and induced mutations. Proton transfer mechanism is a critical phenomenon that is related to the acid-base characteristics of the nucleobases in Watson-Crick base pairs. The energetic and dynamical behavior of the proton can be depicted from these characteristics and their adjustment to the water molecules or the surrounding ions. Further, new pathways open up in which protonated nucleobases are generated by proton transfer from the ionized water molecules and elimination of a hydroxyl radical in this review, the analysis will be focused on understanding the mechanism of untargeted mutations in canonical, wobble, Hoogsteen pairs, and mutagenic tautomers through the non-covalent interactions. Further, rare tautomer formation through the single proton transfer (SPT) and the double proton transfer (DPT), quantum tunneling in nucleobases, radiation-induced bystander effects, role of water in proton transfer (PT) reactions, PT in anticancer drugs-DNA interaction, displacement and oriental polarization, possible models for mutations in DNA, genome instability, and role of proton transfer using kinetic parameters for RNA will be discussed.
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3
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Wang W, Marshall M, Collins E, Marquez S, Mu C, Bowen KH, Zhang X. Intramolecular electron-induced proton transfer and its correlation with excited-state intramolecular proton transfer. Nat Commun 2019; 10:1170. [PMID: 30862822 PMCID: PMC6414547 DOI: 10.1038/s41467-019-09154-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 02/20/2019] [Indexed: 11/09/2022] Open
Abstract
Electron-induced proton transfer depicts the proton motion coupled with the attachment of a low-energy electron to a molecule, which helps to understand copious fundamental chemical processes. Intramolecular electron-induced proton transfer is a similar process that occurs within a single molecule. To date, there is only one known intramolecular example, to the best of our knowledge. By studying the 10-hydroxybenzo[h]quinoline and 8-hydroxyquinoline molecules using anion photoelectron spectroscopy and density functional theory, and by theoretical screening of six other molecules, here we show the intramolecular electron-induced proton transfer capability of a long list of molecules that meanwhile have the excited-state intramolecular proton transfer property. Careful examination of the intrinsic electronic signatures of these molecules reveals that these two distinct processes should occur to the same category of molecules. Intramolecular electron-induced proton transfer could have potential applications such as molecular devices that are responsive to electrons or current.
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Affiliation(s)
- Wei Wang
- Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, 300071, Tianjin, China
| | - Mary Marshall
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Evan Collins
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Sara Marquez
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Chaonan Mu
- Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, 300071, Tianjin, China
| | - Kit H Bowen
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.
| | - Xinxing Zhang
- Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, 300071, Tianjin, China.
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4
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Stephansen AB, King SB, Yokoi Y, Minoshima Y, Li WL, Kunin A, Takayanagi T, Neumark DM. Dynamics of dipole- and valence bound anions in iodide-adenine binary complexes: A time-resolved photoelectron imaging and quantum mechanical investigation. J Chem Phys 2016; 143:104308. [PMID: 26374036 DOI: 10.1063/1.4929995] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Dipole bound (DB) and valence bound (VB) anions of binary iodide-adenine complexes have been studied using one-color and time-resolved photoelectron imaging at excitation energies near the vertical detachment energy. The experiments are complemented by quantum chemical calculations. One-color spectra show evidence for two adenine tautomers, the canonical, biologically relevant A9 tautomer and the A3 tautomer. In the UV-pump/IR-probe time-resolved experiments, transient adenine anions can be formed by electron transfer from the iodide. These experiments show signals from both DB and VB states of adenine anions formed on femto- and picosecond time scales, respectively. Analysis of the spectra and comparison with calculations suggest that while both the A9 and A3 tautomers contribute to the DB signal, only the DB state of the A3 tautomer undergoes a transition to the VB anion. The VB anion of A9 is higher in energy than both the DB anion and the neutral, and the VB anion is therefore not accessible through the DB state. Experimental evidence of the metastable A9 VB anion is instead observed as a shape resonance in the one-color photoelectron spectra, as a result of UV absorption by A9 and subsequent electron transfer from iodide into the empty π-orbital. In contrast, the iodide-A3 complex constitutes an excellent example of how DB states can act as doorway state for VB anion formation when the VB state is energetically available.
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Affiliation(s)
- Anne B Stephansen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark
| | - Sarah B King
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Yuki Yokoi
- Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan
| | - Yusuke Minoshima
- Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan
| | - Wei-Li Li
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Alice Kunin
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Toshiyuki Takayanagi
- Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan
| | - Daniel M Neumark
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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5
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Wang S, Zhao P, Zhang C, Bu Y. The Equally Important Role of Adenine Derivatives to That of Pyrimidine Derivatives in Near‐0 eV Electron‐Induced DNA Lesions. Chemphyschem 2016; 17:1669-77. [DOI: 10.1002/cphc.201600002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Indexed: 01/27/2023]
Affiliation(s)
- Shoushan Wang
- Institute of Theoretical Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan 250100 P. R. China
| | - Peiwen Zhao
- Institute of Theoretical Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan 250100 P. R. China
| | - Changzhe Zhang
- Institute of Theoretical Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan 250100 P. R. China
| | - Yuxiang Bu
- Institute of Theoretical Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan 250100 P. R. China
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6
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Carelli F, Franz J, Gianturco FA. Dipole-driven dynamics for near-threshold electron/positron interactions with pyrimidinic DNA bases: a path to compound formations. Mol Phys 2016. [DOI: 10.1080/00268976.2015.1092609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- F. Carelli
- Institut für Ionen Physik und Angewandte Physik, Leopold-Franzens-Universität, Innsbruck, Austria
| | - J. Franz
- Department of Theoretical Physics and Quantum Informatics, Faculty of Applied Physics and Mathematics, Gdansk University of Technology, ul. Narutowicza 11/12, PL 80-233 Gdansk, Poland
| | - F. A. Gianturco
- Institut für Ionen Physik und Angewandte Physik, Leopold-Franzens-Universität, Innsbruck, Austria
- Scuola Normale Superiore. P.zza de’ Cavalieri 7, Pisa, Italy
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7
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Wang Y, Zhang X, Lyapustina S, Nilles MM, Xu S, Graham JD, Bowen KH, Kelly JT, Tschumper GS, Hammer NI. The onset of electron-induced proton-transfer in hydrated azabenzene cluster anions. Phys Chem Chem Phys 2016; 18:704-12. [DOI: 10.1039/c5cp02746b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The prospect that protons from water may be transferred to N-heterocyclic molecules due to the presence of an excess electron is studied in hydrated azabenzene cluster anions using spectroscopy and computational chemistry.
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Affiliation(s)
- Yi Wang
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
| | - Xinxing Zhang
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
| | | | | | - Shoujun Xu
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
| | | | - Kit H. Bowen
- Department of Chemistry
- Johns Hopkins University
- Baltimore
- USA
| | - John T. Kelly
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
| | | | - Nathan I. Hammer
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
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8
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Gu J, Xie Y, Schaefer HF. Benchmarking the Electron Affinity of Uracil. J Chem Theory Comput 2014; 10:609-12. [DOI: 10.1021/ct400958d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jiande Gu
- Drug Design & Discovery Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, CAS, Shanghai 201203, People’s Republic of China
| | - Yaoming Xie
- Center for Computational
Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525, United States
| | - Henry F. Schaefer
- Center for Computational
Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2525, United States
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9
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Storoniak P, Rak J, Ko YJ, Wang H, Bowen KH. Photoelectron spectroscopic and density functional theoretical studies of the 2′-deoxycytidine homodimer radical anion. J Chem Phys 2013; 139:075101. [DOI: 10.1063/1.4817779] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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Hsu SCN, Wang TP, Kao CL, Chen HF, Yang PY, Chen HY. Theoretical Study of the Protonation of the One-Electron-Reduced Guanine–Cytosine Base Pair by Water. J Phys Chem B 2013; 117:2096-105. [DOI: 10.1021/jp400299v] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Sodio C. N. Hsu
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Tzu-Pin Wang
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Chai-Lin Kao
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Hui-Fen Chen
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Po-Yu Yang
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Hsing-Yin Chen
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
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11
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Ko YJ, Storoniak P, Wang H, Bowen KH, Rak J. Photoelectron spectroscopy and density functional theory studies on the uridine homodimer radical anions. J Chem Phys 2012. [PMID: 23206036 DOI: 10.1063/1.4767053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We report the photoelectron spectrum (PES) of the homogeneous dimer anion radical of uridine, (rU)(2)(●-). It features a broad band consisting of an onset of ∼1.2 eV and a maximum at the electron binding energy (EBE) ranging from 2.0 to 2.5 eV. Calculations performed at the B3LYP∕6-31++G∗∗ level of theory suggest that the PES is dominated by dimeric radical anions in which one uridine nucleoside, hosting the excess charge on the base moiety, forms hydrogen bonds via its O8 atom with hydroxyl of the other neutral nucleoside's ribose. The calculated adiabatic electron affinities (AEAGs) and vertical detachment energies (VDEs) of the most stable homodimers show an excellent agreement with the experimental values. The anionic complexes consisting of two intermolecular uracil-uracil hydrogen bonds appeared to be substantially less stable than the uracil-ribose dimers. Despite the fact that uracil-uracil anionic homodimers are additionally stabilized by barrier-free electron-induced proton transfer, their relative thermodynamic stabilities and the calculated VDEs suggest that they do not contribute to the experimental PES spectrum of (rU)(2)(●-).
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Affiliation(s)
- Yeon Jae Ko
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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12
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Streit L, Dolgounitcheva O, Zakrzewski VG, Ortiz JV. Valence and diffuse-bound anions of noble-gas complexes with uracil. J Chem Phys 2012. [DOI: 10.1063/1.4766735] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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13
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Storoniak P, Rak J, Ko YJ, Wang H, Bowen KH. Photoelectron Spectroscopy and Computational Modeling of Thymidine Homodimer Anions. J Phys Chem B 2012; 116:13975-81. [DOI: 10.1021/jp307570p] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Piotr Storoniak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952
Gdańsk, Poland
| | - Janusz Rak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952
Gdańsk, Poland
| | - Yeon Jae Ko
- Department
of Chemistry, Johns Hopkins University,
Baltimore, Maryland 21218,
United States
| | - Haopeng Wang
- Department
of Chemistry, Johns Hopkins University,
Baltimore, Maryland 21218,
United States
| | - Kit H. Bowen
- Department
of Chemistry, Johns Hopkins University,
Baltimore, Maryland 21218,
United States
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14
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Gu J, Leszczynski J, Schaefer HF. Interactions of electrons with bare and hydrated biomolecules: from nucleic acid bases to DNA segments. Chem Rev 2012; 112:5603-40. [PMID: 22694487 DOI: 10.1021/cr3000219] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Jiande Gu
- Drug Design & Discovery Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, CAS, PR China.
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15
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Chen HY, Yeh SW, Hsu SCN, Kao CL, Dong TY. Effect of nucleobase sequence on the proton-transfer reaction and stability of the guanine–cytosine base pair radical anion. Phys Chem Chem Phys 2011; 13:2674-81. [DOI: 10.1039/c0cp01419b] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Szyperska A, Gajewicz A, Mazurkiewicz K, Leszczynski J, Rak J. Theoretical studies on interactions between low energy electrons and protein–DNA fragments: valence anions of AT-amino acids side chain complexes. Phys Chem Chem Phys 2011; 13:19499-507. [DOI: 10.1039/c1cp21511f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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17
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Kumar A, Sevilla MD. Proton-coupled electron transfer in DNA on formation of radiation-produced ion radicals. Chem Rev 2010; 110:7002-23. [PMID: 20443634 PMCID: PMC2947616 DOI: 10.1021/cr100023g] [Citation(s) in RCA: 172] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, MI 48309
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18
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Ko YJ, Wang H, Radisic D, Stokes ST, Eustis SN, Bowen KH, Mazurkiewicz K, Storoniak P, Kowalczyk A, Haranczyk M, Gutowski M, Rak J. Barrier-free proton transfer induced by electron attachment to the complexes between 1‐methylcytosine and formic acid. Mol Phys 2010. [DOI: 10.1080/00268976.2010.515623] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Yeon Jae Ko
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Haopeng Wang
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Dunja Radisic
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Sarah T. Stokes
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Soren N. Eustis
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Kit H. Bowen
- a Department of Chemistry , Johns Hopkins University , Baltimore , MD 21218 , USA
| | - Kamil Mazurkiewicz
- b Department of Chemistry , University of Gdańsk , Sobieskiego 18 , 80-952 Gdańsk , Poland
| | - Piotr Storoniak
- b Department of Chemistry , University of Gdańsk , Sobieskiego 18 , 80-952 Gdańsk , Poland
| | - Arkadiusz Kowalczyk
- b Department of Chemistry , University of Gdańsk , Sobieskiego 18 , 80-952 Gdańsk , Poland
| | - Maciej Haranczyk
- c Computational Research Division, Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA
| | - Maciej Gutowski
- d Chemistry-School of Engineering and Physical Sciencs, Heriot-Watt University , Edinburgh EH14 4AS , UK
| | - Janusz Rak
- b Department of Chemistry , University of Gdańsk , Sobieskiego 18 , 80-952 Gdańsk , Poland
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19
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Storoniak P, Mazurkiewicz K, Haranczyk M, Gutowski M, Rak J, Eustis SN, Ko YJ, Wang H, Bowen KH. The Anionic (9-Methyladenine)−(1-Methylthymine) Base Pair Solvated by Formic Acid. A Computational and Photoelectron Spectroscopy Study. J Phys Chem B 2010; 114:11353-62. [DOI: 10.1021/jp104668h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Piotr Storoniak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Kamil Mazurkiewicz
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Maciej Haranczyk
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Maciej Gutowski
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Janusz Rak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Soren N. Eustis
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Yeon Jae Ko
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Haopeng Wang
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Kit H. Bowen
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail Stop 50F-1650, Berkeley, California 94720-8139, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K., and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
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20
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Szyperska A, Rak J, Leszczynski J, Li X, Ko YJ, Wang H, Bowen KH. Low-Energy-Barrier Proton Transfer Induced by Electron Attachment to the Guanine⋅⋅⋅Cytosine Base Pair. Chemphyschem 2010; 11:880-8. [DOI: 10.1002/cphc.200900810] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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21
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Chen HY, Hsu SCN, Kao CL. Microhydration of 9-methylguanine:1-methylcytosinebase pair and its radical anion: a density functional theory study. Phys Chem Chem Phys 2010; 12:1253-63. [DOI: 10.1039/b920603e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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22
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Chen HY, Young PY, Hsu SCN. Theoretical evidence of barrier-free proton transfer in 7-azaindole-water cluster anions. J Chem Phys 2009; 130:165101. [DOI: 10.1063/1.3120604] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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23
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Szyperska A, Rak J, Leszczynski J, Li X, Ko YJ, Wang H, Bowen KH. Valence Anions of 9-Methylguanine−1-Methylcytosine Complexes. Computational and Photoelectron Spectroscopy Studies. J Am Chem Soc 2009; 131:2663-9. [DOI: 10.1021/ja808313e] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Anna Szyperska
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Janusz Rak
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Jerzy Leszczynski
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Xiang Li
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Yeon Jae Ko
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Haopeng Wang
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
| | - Kit H. Bowen
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland, Interdisciplinary Nanotoxicity Center, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218
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24
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Kobyłecka M, Leszczynski J, Rak J. Valence anion of thymine in the DNA pi-stack. J Am Chem Soc 2008; 130:15683-7. [PMID: 18954049 DOI: 10.1021/ja806251h] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Most of theoretical data on the stability of radical anions supported by nucleic acid bases have been obtained for anions of isolated nucleobases, their nucleosides, or nucleotides. This approach ignores the hallmark forces of DNA, namely, hydrogen bonding and pi-stacking interactions. Since these interactions might be crucial for the electron affinities of nucleobases bound in DNA, we report for the first time on the stability of the thymine valence anion in trimers of complementary bases possessing the regular B-DNA geometry but differing in base sequence. In order to estimate the energetics of electron attachment to a trimer, we developed a thermodynamic cycle employing all possible two-body interaction energies in the neutral and anionic duplex as well as the adiabatic electron affinity of isolated thymine. All calculations were carried out at the MP2 level of theory with the aug-cc-pVDZ basis set. The two-body interaction energies were corrected for the basis set superposition error, and in benchmark systems, they were extrapolated to the basis set limit and supplemented with correction for higher order correlation terms calculated at the CCSD(T) level. We have demonstrated that the sequence of nucleic bases has a profound effect on the stability of the thymine valence anion: the anionic 5'-CTC-3' (6.0 kcal/mol) sequence is the most stable configuration, and the 5'-GTG-3' (-8.0 kcal/mol) trimer anion is the most unstable species. On the basis of obtained results, one can propose DNA sequences that are different in their vulnerability to damage by low energy electron.
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Affiliation(s)
- Monika Kobyłecka
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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25
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Bachorz RA, Klopper W, Gutowski M, Li X, Bowen KH. Photoelectron spectrum of valence anions of uracil and first-principles calculations of excess electron binding energies. J Chem Phys 2008; 129:054309. [PMID: 18698902 DOI: 10.1063/1.2965128] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The photoelectron spectrum (PES) of the uracil anion is reported and discussed from the perspective of quantum chemical calculations of the vertical detachment energies (VDEs) of the anions of various tautomers of uracil. The PES peak maximum is found at an electron binding energy of 2.4 eV, and the width of the main feature suggests that the parent anions are in a valence rather than a dipole-bound state. The canonical tautomer as well as four tautomers that result from proton transfer from an NH group to a C atom were investigated computationally. At the Hartree-Fock and second-order Moller-Plesset perturbation theory levels, the adiabatic electron affinity (AEA) and the VDE have been converged to the limit of a complete basis set to within +/-1 meV. Post-MP2 electron-correlation effects have been determined at the coupled-cluster level of theory including single, double, and noniterative triple excitations. The quantum chemical calculations suggest that the most stable valence anion of uracil is the anion of a tautomer that results from a proton transfer from N1H to C5. It is characterized by an AEA of 135 meV and a VDE of 1.38 eV. The peak maximum is as much as 1 eV larger, however, and the photoelectron intensity is only very weak at 1.38 eV. The PES does not lend support either to the valence anion of the canonical tautomer, which is the second most stable anion, and whose VDE is computed at about 0.60 eV. Agreement between the peak maximum and the computed VDE is only found for the third most stable tautomer, which shows an AEA of approximately -0.1 eV and a VDE of 2.58 eV. This tautomer results from a proton transfer from N3H to C5. The results illustrate that the characteristics of biomolecular anions are highly dependent on their tautomeric form. If indeed the third most stable anion is observed in the experiment, then it remains an open question why and how this species is formed under the given conditions.
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Affiliation(s)
- Rafał A Bachorz
- Center for Functional Nanostructures (CFN) and Lehrstuhl für Theoretische Chemie, Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany
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26
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Kobyłecka M, Gu J, Rak J, Leszczynski J. Barrier-free proton transfer in the valence anion of 2'-deoxyadenosine-5'-monophosphate. II. A computational study. J Chem Phys 2008; 128:044315. [PMID: 18247957 DOI: 10.1063/1.2823002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The propensity of four representative conformations of 2(')-deoxyadenosine-5(')-monophosphate (5(')-dAMPH) to bind an excess electron has been studied at the B3LYP6-31++G(d,p) level. While isolated canonical adenine does not support stable valence anions in the gas phase, all considered neutral conformations of 5(')-dAMPH form adiabatically stable anions. The type of an anionic 5(')-dAMPH state, i.e., the valence, dipole bound, or mixed (valence/dipole bound), depends on the internal hydrogen bond(s) pattern exhibited by a particular tautomer. The most stable anion results from an electron attachment to the neutral syn-south conformer. The formation of this anion is associated with a barrier-free proton transfer triggered by electron attachment and the internal rotation around the C4(')-C5(') bond. The adiabatic electron affinity of the a_south-syn anion is 1.19 eV, while its vertical detachment energy is 1.89 eV. Our results are compared with the photoelectron spectrum (PES) of 5(')-dAMPH(-) measured recently by Stokes et al., [J. Chem. Phys. 128, 044314 (2008)]. The computational VDE obtained for the most stable anionic structure matches well with the experimental electron binding energy region of maximum intensity. A further understanding of DNA damage might require experimental and computational studies on the systems in which purine nucleotides are engaged in hydrogen bonding.
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Affiliation(s)
- Monika Kobyłecka
- Faculty of Chemistry, University of Gdańsk, 80-952 Gdańsk, Sobieskiego 18, Poland
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27
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First-principle applications on protonated adenine dimers with N–H⋯N intermolecular coupling. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.theochem.2007.09.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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28
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Stable Valence Anions of Nucleic Acid Bases and DNA Strand Breaks Induced by Low Energy Electrons. CHALLENGES AND ADVANCES IN COMPUTATIONAL CHEMISTRY AND PHYSICS 2008. [DOI: 10.1007/978-1-4020-8184-2_21] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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29
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Haranczyk M, Gutowski M, Li X, Bowen KH. Adiabatically Bound Valence Anions of Guanine. J Phys Chem B 2007; 111:14073-6. [DOI: 10.1021/jp077439z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Maciej Haranczyk
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom, and Departments of Chemistry and Materials Science, Johns Hopkins University, Baltimore, Maryland 21218
| | - Maciej Gutowski
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom, and Departments of Chemistry and Materials Science, Johns Hopkins University, Baltimore, Maryland 21218
| | - Xiang Li
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom, and Departments of Chemistry and Materials Science, Johns Hopkins University, Baltimore, Maryland 21218
| | - Kit H. Bowen
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland, Chemistry-School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom, and Departments of Chemistry and Materials Science, Johns Hopkins University, Baltimore, Maryland 21218
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30
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Mazurkiewicz K, Haranczyk M, Storoniak P, Gutowski M, Rak J, Radisic D, Eustis SN, Wang D, Bowen KH. Intermolecular proton transfer induced by excess electron attachment to adenine(formic acid)n (n=2, 3) hydrogen-bonded complexes. Chem Phys 2007. [DOI: 10.1016/j.chemphys.2007.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Jayatilaka N, Nelson WH. Structure of Radicals from X-Irradiated Guanine Derivatives. 2. An Experimental and Computational Study of 9-Ethylguanine Single Crystals. J Phys Chem B 2007; 111:7887-96. [PMID: 17571877 DOI: 10.1021/jp0712147] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
An EPR (electron paramagnetic resonance) and ENDOR (electron-nuclear double resonance) study of 9-ethylguanine crystals X-irradiated at 10 K detected evidence for three radical forms. Radical R1, characterized by three proton and two nitrogen hyperfine interactions, was identified as the product of net hydrogenation at N7 of the guanine unit. R1, which evidently formed by protonation of the primary electron addition product, exhibited an unusually distorted structure leading to net positive isotropic components of the alpha-coupling to the hydrogen attached to C8 of the guanine unit. Radical R2, characterized by two nitrogen and three proton hyperfine couplings, was identified as the primary electron loss product, *G+. Distinguishing between *G+ and its N1-deprotonated product is difficult because their couplings are so similar, and density functional theory (DFT) calculations were indispensable for doing so. The results for R2 provide the most complete ENDOR characterization of *G+ presented so far. Radical R3 exhibited a narrow EPR pattern but could not be identified. The identification of radicals R1 and R2 was supported by DFT calculations using the B3LYP/6-311+G(2df,p)//6-31+G(d,p) approach. Radical R4, detected after irradiation of the crystals at room temperature, was identified as the well-known product of net hydrogenation at C8 of the guanine component. Spectra from the room temperature irradiation contained evidence for R5, an additional radical that could not be identified. Radical concentrations from the low temperature irradiation were estimated as follows: R1, 20%; R2, 65%; R3, 15%.
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Affiliation(s)
- Nayana Jayatilaka
- Department of Physics and Astronomy, Georgia State University, P.O. Box 4106, Atlanta, Georgia 30302-4106, USA
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32
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Funston AM, Lymar SV, Saunders-Price B, Czapski G, Miller JR. Rate and Driving Force for Protonation of Aryl Radical Anions in Ethanol. J Phys Chem B 2007; 111:6895-902. [PMID: 17523623 DOI: 10.1021/jp071450h] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Aryl radical anions created in liquid alcohols decay on the microsecond time scale by transfer of protons from the solvent. This paper reports a 4.5 decade range of rate constants for proton transfer from a single weak acid, ethanol, to a series of unsubstituted aryl radical anions, Ar-*. The rate constants correlate with free energy change, DeltaG(o), despite wide variations in the two factors that contribute to DeltaG(o): (a) the reduction potentials of the aryls and (b) the Ar-H* bond strengths in the product radicals. For aryl radical anions containing CH2OH substituents, such as 2,2'-biphenyldimethanol*- which is protonated with a rate constant of 3x10(9) s(-1), the faster rates do not fit well in the free energy correlation, suggesting a change in mechanism.
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Affiliation(s)
- Alison M Funston
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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33
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Kumar A, Sevilla MD. Low-energy electron attachment to 5'-thymidine monophosphate: modeling single strand breaks through dissociative electron attachment. J Phys Chem B 2007; 111:5464-74. [PMID: 17429994 DOI: 10.1021/jp070800x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mechanisms of low-energy electron (LEE) attachment and subsequent single-strand break (SSB) formation are investigated by density functional theory treatment of a simple model for DNA, i.e., the nucleotide, 5'-thymidine monophosphate (5'-dTMPH). In the present study, the C5'-O5' bond dissociation due to LEE attachment has been followed along the adiabatic as well as on the vertical (electron attached to the optimized geometry of the neutral molecule) anionic surfaces using B3LYP functional and 6-31G* and 6-31++G** basis sets. Surprisingly, it is found that the PES of C5'-O5' bond dissociation in the anion radicals have approximately the same barrier for both adiabatic and vertical pathways. These results provide support for the hypothesis that transiently bound electrons (shape resonances) to the virtual molecular orbitals of the neutral molecule likely play a key role in the cleavage of the sugar-phosphate C5'-O5' bond in DNA resulting in the direct formation of single strand breaks without significant molecular relaxation. To take into account the solvation effects, we considered the neutral and anion radical of 5'-dTMP surrounded by 5 or 11 water molecules with Na+ as a counterion. These structures were optimized using the B3LYP/6-31G** level of theory. We find the barrier height for adiabatic C5'-O5' bond dissociation of 5'-dTMP anion radical in aqueous environment is so substantially higher than in the gas phase that the adiabatic route will not contribute to DNA strand cleavage in aqueous systems. This result is in agreement with experiment.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA
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34
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Harańczyk M, Gutowski M, Li X, Bowen KH. Bound anionic states of adenine. Proc Natl Acad Sci U S A 2007; 104:4804-7. [PMID: 17360375 PMCID: PMC1829219 DOI: 10.1073/pnas.0609982104] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Indexed: 11/18/2022] Open
Abstract
Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the newfound anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The new valence states observed here, unlike the dipole-bound state, could exist in condensed phases and might be relevant to radiobiological damage. The discovery of these valence anionic states of adenine was facilitated by the development of (i) an experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a combinatorial/quantum chemical approach for identification of the most stable tautomers of organic molecules.
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Affiliation(s)
- Maciej Harańczyk
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland
| | - Maciej Gutowski
- Department of Chemistry, University of Gdańsk, 80-952 Gdańsk, Poland
- Chemistry–School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh EH14 4AS, United Kingdom
- Chemical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352; and
| | - Xiang Li
- Departments of Chemistry and Materials Science, The Johns Hopkins University, Baltimore, MD 21218
| | - Kit H. Bowen
- Departments of Chemistry and Materials Science, The Johns Hopkins University, Baltimore, MD 21218
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