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Bauer B, Sharma R, Chergui M, Oppermann M. Exciton decay mechanism in DNA single strands: back-electron transfer and ultrafast base motions. Chem Sci 2022; 13:5230-5242. [PMID: 35655577 PMCID: PMC9093102 DOI: 10.1039/d1sc06450a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 04/09/2022] [Indexed: 12/03/2022] Open
Abstract
The photochemistry of DNA systems is characterized by the ultraviolet (UV) absorption of π-stacked nucleobases, resulting in exciton states delocalized over several bases. As their relaxation sensitively depends on local stacking conformations, disentangling the ensuing electronic and structural dynamics has remained an experimental challenge, despite their fundamental role in protecting the genome from potentially harmful UV radiation. Here we use transient absorption and transient absorption anisotropy spectroscopy with broadband femtosecond deep-UV pulses (250–360 nm) to resolve the exciton dynamics of UV-excited adenosine single strands under physiological conditions. Due to the exceptional deep-UV bandwidth and polarization sensitivity of our experimental approach, we simultaneously resolve the population dynamics, charge-transfer (CT) character and conformational changes encoded in the UV transition dipoles of the π-stacked nucleotides. Whilst UV excitation forms fully charge-separated CT excitons in less than 0.3 ps, we find that most decay back to the ground state via a back-electron transfer. Based on the anisotropy measurements, we propose that this mechanism is accompanied by a structural relaxation of the photoexcited base-stack, involving an inter-base rotation of the nucleotides. Our results finally complete the exciton relaxation mechanism for adenosine single strands and offer a direct view into the coupling of electronic and structural dynamics in aggregated photochemical systems. Despite its key role in DNA photochemistry, the decay mechanism of excitons in stacked bases has remained difficult to resolve. Ultrafast polarization spectroscopy now reveals a back-electron transfer and ultrafast base motions in adenosine strands.![]()
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Affiliation(s)
- Benjamin Bauer
- Laboratory of Ultrafast Spectroscopy (LSU), Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC-FSB CH-1015 Lausanne Switzerland
| | - Rahul Sharma
- Laboratory for Computation and Visualization in Mathematics and Mechanics, École Polytechnique Fédérale de Lausanne, MATH-FSB CH-1015 Lausanne Switzerland
| | - Majed Chergui
- Laboratory of Ultrafast Spectroscopy (LSU), Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC-FSB CH-1015 Lausanne Switzerland
| | - Malte Oppermann
- Laboratory of Ultrafast Spectroscopy (LSU), Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne, ISIC-FSB CH-1015 Lausanne Switzerland
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2
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Diamantis P, Tavernelli I, Rothlisberger U. Redox Properties of Native and Damaged DNA from Mixed Quantum Mechanical/Molecular Mechanics Molecular Dynamics Simulations. J Chem Theory Comput 2020; 16:6690-6701. [PMID: 32926773 DOI: 10.1021/acs.jctc.0c00568] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The redox properties of two large DNA fragments composed of 39 base pairs, differing only by an 8-oxoguanine (8oxoG) defect replacing a guanine (G), were investigated in physiological conditions using mixed quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations. The quantum region of the native fragment comprised 3 G-C base pairs, while one G was replaced by an 8oxoG in the defect fragment. The calculated values for the redox free energy are 6.55 ± 0.28 eV and 5.62 ± 0.30 eV for the native and the 8oxoG-containing fragment, respectively. The respective estimates for the reorganization free energy are 1.25 ± 0.18 eV and 1.00 ± 0.18 eV. Both reactions follow the Marcus theory for electron transfer. The large difference in redox potential between the two fragments shows that replacement of a G by an 8oxoG renders the DNA more easily oxidizable. This finding is in agreement with the suggestion that DNA fragments containing an 8oxoG defect can act as sinks of oxidative damage that protect the rest of the genome from assault. In addition, the difference in redox potential between the native and the defect DNA fragment indicates that a charge transfer-based mechanism for the recognition of DNA defects might be feasible, in line with recent suggestions based on experimental observations.
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Affiliation(s)
- Polydefkis Diamantis
- Laboratory of Computational Chemistry and Biochemistry, École Polytechnique Fédérale de Lausanne, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
| | - Ivano Tavernelli
- Laboratory of Computational Chemistry and Biochemistry, École Polytechnique Fédérale de Lausanne, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
| | - Ursula Rothlisberger
- Laboratory of Computational Chemistry and Biochemistry, École Polytechnique Fédérale de Lausanne, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland
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3
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Diamantis P, Tavernelli I, Rothlisberger U. Vertical Ionization Energies and Electron Affinities of Native and Damaged DNA Bases, Nucleotides, and Pairs from Density Functional Theory Calculations: Model Assessment and Implications for DNA Damage Recognition and Repair. J Chem Theory Comput 2019; 15:2042-2052. [PMID: 30681847 DOI: 10.1021/acs.jctc.8b00645] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
To assess the effect of an 8-oxoguanine (8OG) defect base on the vertical ionization energies (VIEs) and electron affinities (VEAs) of DNA, density functional theory calculations were carried out for native and defect DNA bases and nucleotides, as well as for larger fragments containing one or multiple pairs. Absolute values of VIE and VEA under implicit solvation did not converge as a function of model size even up to the largest systems taken into consideration (3 base pairs/2 nucleotide pairs). Nonetheless, a consistent trend was observed for the relative difference in the VIE of native and damaged DNA showing that the defect was lowering the VIE by -0.1 eV for the largest fragments. This strongly suggests that the presence of 8OG makes the DNA more easily oxidizable and is in line with experimental evidence that a defect region can act as a sink of oxidative damage. In contrast, relative differences in VEA were very small and varied inconsistently around 0.01 eV. This seems to indicate that insertion of 8OG has a negligible effect on the electron capturing properties of DNA. Similar conclusions can be drawn by the adiabatic IEs and EAs computed for some of the larger fragments. Analysis of the hole and excess electron distributions was consistent with the above trends. The findings presented here support the possibility that a mechanism based on hole transport through DNA may be efficiently employed by the cell for the detection of defect bases.
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Affiliation(s)
- Polydefkis Diamantis
- Laboratory of Computational Chemistry and Biochemistry , École Polytechnique Fédérale de Lausanne , Swiss Federal Institute of Technology, CH-1015 Lausanne , Switzerland
| | - Ivano Tavernelli
- Laboratory of Computational Chemistry and Biochemistry , École Polytechnique Fédérale de Lausanne , Swiss Federal Institute of Technology, CH-1015 Lausanne , Switzerland
| | - Ursula Rothlisberger
- Laboratory of Computational Chemistry and Biochemistry , École Polytechnique Fédérale de Lausanne , Swiss Federal Institute of Technology, CH-1015 Lausanne , Switzerland
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4
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Kohanoff J, McAllister M, Tribello GA, Gu B. Interactions between low energy electrons and DNA: a perspective from first-principles simulations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:383001. [PMID: 28617676 DOI: 10.1088/1361-648x/aa79e3] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts with the interaction of radiation-either photons or swift ions-and the biological medium, which causes electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals. Both of these species can cause damage to biological molecules, in particular DNA. In the long run, this molecular level damage can prevent cells from replicating and can hence lead to cell death. For a long time it was assumed that the main actors in the damage process were the radicals. However, experiments in a seminal paper by the group of Leon Sanche in 2000 showed that low-energy electrons (LEE), such as those generated when ionising biological targets, can also cause bond breaks in biomolecules, and strand breaks in plasmid DNA in particular (Boudaiffa et al 2000 Science 287 1658-60). These results prompted a significant amount of experimental and theoretical work aimed at elucidating the role played by LEE in DNA damage. In this Topical Review we provide a general overview of the problem. We discuss experimental findings and theoretical results hand in hand with the aim of describing the physics and chemistry that occurs during the process of radiation damage, from the initial stages of electronic excitation, through the inelastic propagation of electrons in the medium, the interaction of electrons with DNA, and the chemical end-point effects on DNA. A very important aspect of this discussion is the consideration of a realistic, physiological environment. The role played by the aqueous solution and the amino acids from the histones in chromatin must be considered. Moreover, thermal fluctuations must be incorporated when studying these phenomena. Hence, a special place in this Topical Review is occupied by our recent first-principles molecular dynamics simulations that address the issue of how the environment favours or prevents LEEs from causing damage to DNA. We finish by summarising the conclusions achieved so far, and by suggesting a number of possible directions for further study.
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Affiliation(s)
- Jorge Kohanoff
- Atomistic Simulation Centre, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
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5
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Martínez-Cifuentes M, Salazar R, Escobar CA, Weiss-López BE, Santos LS, Araya-Maturana R. Correlating experimental electrochemistry and theoretical calculations in 2′-hydroxy chalcones: the role of the intramolecular hydrogen bond. RSC Adv 2015. [DOI: 10.1039/c5ra10140a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The molecular structure and electrochemical behaviour of a series of 2′-hydroxychalcones were studied. Results show the importance of the intramolecular hydrogen bond and the methoxy substituent pattern on the redox properties of these compounds.
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Affiliation(s)
| | - Ricardo Salazar
- Laboratorio de Electroquímica MedioAmbiental
- LEQMA
- Departamento de Química de los Materiales
- Facultad de Química y Biología
- Universidad de Santiago de Chile, USACh
| | - Carlos A. Escobar
- Departamento de Ciencias Químicas
- Universidad Andres Bello
- Santiago
- Chile
| | | | - Leonardo S. Santos
- Laboratorio de Síntesis Asimétrica
- Instituto de Química de los Recursos Naturales
- Universidad de Talca
- Talca
- Chile
| | - Ramiro Araya-Maturana
- Departamento de Química Orgánica y Fisicoquímica
- Facultad de Ciencias Químicas Y Farmacéuticas
- Universidad de Chile
- Santiago 1
- Chile
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6
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Shao P, Kuang XY, Ding LP, Zhao YR. Structures, electrophilic properties, and hydrogen bonds of cytidine, uridine, and their radical anions: Microhydration effects. J Chem Phys 2013; 139:024305. [PMID: 23862941 DOI: 10.1063/1.4812500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Structures, electrophilic properties, and hydrogen bonds of the neutral and anionic monohydrated nucleoside, (cytidine)H2O, and (uridine)H2O have been systematically investigated using density functional theory. Various water-binding sites were predicted by explicitly considering the optimized monohydrated structures. Meanwhile, predictions of electron affinities and vertical detachment energies were also carried out to investigate their electrophilic properties. By examining the singly occupied molecular orbital and natural population analysis, we found the excess negative charge is localized on the cytidine and uridine moiety in anionic monohydrates. This may be the reason why the strength of hydrogen bonding undergoes an obvious change upon the extra electron attachment. Based on the electron density (ρ) and reduced density gradient (RDG), we present an approach to map and analyze the weak interaction (especially hydrogen bond) in monohydrated cytidine and uridine. The scatter plots of RDG versus ρ allow us to identify the different type interactions. Meanwhile, the maps of the gradient isosurfaces show a rich visualization of hydrogen bond, van der Waals interaction, and steric effect.
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Affiliation(s)
- Peng Shao
- Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
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7
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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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8
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González-Ramírez I, Segarra-Martí J, Serrano-Andrés L, Merchán M, Rubio M, Roca-Sanjuán D. On the N1-H and N3-H Bond Dissociation in Uracil by Low Energy Electrons: A CASSCF/CASPT2 Study. J Chem Theory Comput 2012; 8:2769-76. [PMID: 26592118 DOI: 10.1021/ct300153f] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dissociative electron-attachment (DEA) phenomena at the N1-H and N3-H bonds observed experimentally at low energies (<3 eV) in uracil are studied with the CASSCF/CASPT2 methodology. Two valence-bound π(-) and two dissociative σ(-) states of the uracil anionic species, together with the ground state of the neutral molecule, are proven to contribute to the shapes appearing in the experimental DEA cross sections. Conical intersections (CI) between the π(-) and σ(-) are established as the structures which activate the DEA processes. The N1-H and N3-H DEA mechanisms in uracil are described, and experimental observations are interpreted on the basis of two factors: (1) the relative energy of the (U-H)(-) + H fragments obtained after DEA with respect to the ground-state equilibrium structure (S0) of the neutral molecule (threshold for DEA) and (2) the relative energy of the CIs also with respect to S0 (band maxima). The π1(-) state is found to be mainly responsible for the N1-H bond breaking, whereas the π2(-) state is proved to be involved in the cleavage of the N3-H bond.
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Affiliation(s)
- Israel González-Ramírez
- Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain
| | - Javier Segarra-Martí
- Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain
| | - Luis Serrano-Andrés
- Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain
| | - Manuela Merchán
- Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain
| | - Mercedes Rubio
- Instituto de Ciencia Molecular, Universitat de València , P.O. Box 22085, 46071 València, Spain
| | - Daniel Roca-Sanjuán
- Department of Chemistry-Ångström, Theoretical Chemistry Program, Uppsala Univeristy , P.O. Box 518, 75120 Uppsala, Sweden
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9
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Chomicz L, Rak J, Paneth P, Sevilla M, Ko YJ, Wang H, Bowen KH. Valence anions of N-acetylproline in the gas phase: computational and anion photoelectron spectroscopic studies. J Chem Phys 2011; 135:114301. [PMID: 21950856 PMCID: PMC3298562 DOI: 10.1063/1.3625957] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 07/28/2011] [Indexed: 11/14/2022] Open
Abstract
We report the photoelectron spectrum of anionic N-acetylproline, (N-AcPro)(-), measured with 3.49 eV photons. This spectrum, which consists of a band centered at an electron binding energy of 1.4 eV and a higher energy spectral tail, confirms that N-acetylproline forms a valence anion in the gas phase. The neutrals and anions of N-AcPro were also studied computationally at the B3LYP∕6-31++G(d,p) level. Based on the calculations, we conclude that the photoelectron spectrum is due to anions which originated from proton transfer induced by electron attachment to the π* orbital localized at the acetyl group of N-AcPro. We also characterized the energetics of reaction paths leading to pyrrolidine ring opening in the anionic N-AcPro. These data suggest that electron induced decomposition of peptides/proteins comprising proline strongly depends on the presence of proton donors in the close vicinity to the proline residue.
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Affiliation(s)
- Lidia Chomicz
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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10
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Radisic D, Ko YJ, Nilles JM, Stokes ST, Sevilla MD, Rak J, Bowen KH. Photoelectron spectroscopic studies of 5-halouracil anions. J Chem Phys 2011; 134:015101. [PMID: 21219027 PMCID: PMC3188609 DOI: 10.1063/1.3525623] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 11/18/2010] [Indexed: 01/19/2023] Open
Abstract
The parent negative ions of 5-chlorouracil, UCl(-) and 5-fluorouracil, UF(-) have been studied using anion photoelectron spectroscopy in order to investigate the electrophilic properties of their corresponding neutral halouracils. The vertical detachment energies (VDE) of these anions and the adiabatic electron affinities (EA) of their neutral molecular counterparts are reported. These results are in good agreement with the results of previously published theoretical calculations. The VDE values for both UCl(-) and UF(-) and the EA values for their neutral molecular counterparts are much greater than the corresponding values for both anionic and neutral forms of canonical uracil and thymine. These results are consistent with the observation that DNA is more sensitive to radiation damage when thymine is replaced by halouracil. While we also attempted to prepare the parent anion of 5-bromouracil, UBr(-), we did not observe it, the mass spectrum exhibiting only Br(-) fragments, i.e., 5-bromouracil apparently underwent dissociative electron attachment. This observation is consistent with a previous assessment, suggesting that 5-bromouracil is the best radio-sensitizer among these three halo-nucleobases.
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Affiliation(s)
- Dunja Radisic
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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11
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Li X, Wang H, Bowen KH. Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine−(H2O)n=0–2, cytidine−(H2O)n=0–2, and thymidine−(H2O)n=0,1. J Chem Phys 2010; 133:144304. [DOI: 10.1063/1.3487735] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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12
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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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13
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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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14
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Kobyłecka M, Leszczynski J, Rak J. Stability of the valence anion of cytosine is governed by nucleobases sequence in the double stranded DNA pi-stack: A computational study. J Chem Phys 2009; 131:085103. [PMID: 19725636 DOI: 10.1063/1.3204939] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The stabilities of the valence anion of cytosine (C(-)) in model trimers of complementary base pairs that possess the B-DNA geometry but differ in base sequence are reported. In order to estimate the energetics of electron attachment to the middle cytosine incorporated in the trimer, 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 cytosine were developed. All calculations were carried out at the MP2 level of theory with the aug-cc-pVDZ basis set. We have demonstrated that contrary to the literature reports, concerning single stranded DNA, the sequence of nucleic bases has a profound effect on the stability of the cytosine valence anion. The anionic 3(')-CCC-5(') complex is the most stable configuration (EA=0.399 eV) and the 3(')-GCG-5(') trimer anion is the most unstable species (EA=-0.193 eV). Moreover, with the energetic correction for the presence of sugar-phosphate backbone all possible double stranded DNA sequences lead to the stable C(-). The predicted electron affinities of the cytosine anion have been compared to the results of analogous studies on the thymine anion published recently [M. Kobyłecka et al., J. Am. Chem. Soc. 130, 15683 (2008)]. The consequences of low-energy barrier proton transfer in the GC anion have been discussed in the context of induced by electrons DNA single strand breaks. The DNA sequences that should dramatically differ in their vulnerability to be damaged by low energy electrons have been proposed.
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Affiliation(s)
- Monika Kobyłecka
- Faculty of Chemistry, University of Gdańsk, 80-952 Gdansk, Poland
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15
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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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16
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Roca-Sanjuán D, Merchán M, Serrano-Andrés L, Rubio M. Ab initio determination of the electron affinities of DNA and RNA nucleobases. J Chem Phys 2009; 129:095104. [PMID: 19044892 DOI: 10.1063/1.2958286] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic electron affinities of the five canonical DNA and RNA nucleobases: uracil, thymine, cytosine, adenine, and guanine. The present results aim for the accurate determination of the intrinsic electron acceptor properties of the isolated nucleic acid bases as described by their electron affinities, establishing an overall set of theoretical reference values at a level not reported before and helping to rule out less reliable theoretical and experimental data and to calibrate theoretical strategies.
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Affiliation(s)
- Daniel Roca-Sanjuán
- Instituto de Ciencia Molecular, Universitat de Valencia, Apartado 22085, ES-46071 Valencia, Spain
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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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18
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Stokes ST, Grubisic A, Li X, Ko YJ, Bowen KH. Photoelectron spectroscopy of the parent anions of the nucleotides, adenosine-5'-monophosphate and 2'deoxyadenosine-5'-monophosphate. J Chem Phys 2008; 128:044314. [PMID: 18247956 DOI: 10.1063/1.2823001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The parent anions of the nucleotides, adenosine-5(')-monophosphate (AMPH) and 2(')deoxyadenosine-5(')-monophosphate (dAMPH) were generated in a novel source and their photoelectron spectra recorded with 3.49 eV photons. Vertical detachment energy (VDE) and the adiabatic electron affinity (EA(a)) values were extracted from each of the two spectra. Concurrently, Kobylecka et al. [J. Chem. Phys. 128, 044315 (2008)] conducted calculations which explored electron attachment to dAMPH. Based on the agreement between their calculated and our measured VDE and EA(a) values, we conclude that the dAMPH(-) anions studied in these experiments were formed by electron-induced, intramolecular, (barrier-free) proton-transfer as predicted by the calculations. Given the similarities between the photoelectron spectra of dAMPH(-) and AMPH(-), it is likely that AMPH(-) can be described in the same manner.
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Affiliation(s)
- Sarah T Stokes
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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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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20
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Kumar A, Sevilla MD, Suhai S. Microhydration of the guanine-cytosine (GC) base pair in the neutral and anionic radical states: a density functional study. J Phys Chem B 2008; 112:5189-98. [PMID: 18380501 DOI: 10.1021/jp710957p] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A density functional study of the effects of microhydration on the guanine-cytosine (GC) base pair and its anion radical is presented. Geometries of the GC base pair in the presence of 6 and 11 water molecules were fully optimized in the neutral (GC-nH2O) and anion radical [(GC-nH2O)*-] (n = 6 and 11) states using the B3LYP method and the 6-31+G** basis set. Further, vibrational frequency analysis at the same level of theory (B3LYP/6-31+G**) was also performed to ensure the existence of local minima in these hydrated structures. It was found that water molecules surrounding the GC base pair have significant effects on the geometry of the GC base pair and promote nonplanarity in the GC base pair. The calculated structures were found to be in good agreement with those observed experimentally and obtained in molecular dynamics (MD) simulation studies. The water molecules in neutral GC-nH2O complexes lie near the ring plane of the GC base pair where they undergo hydrogen bonding with both GC and each other. However, in the GC anion radical complexes (GC-nH2O, n = 6, 11), the water molecules are displaced substantially from the GC ring plane. For GC-11H2O*-, a water molecule is hydrogen-bonded with the C6 atom of the cytosine base. We found that the hydration shell initially destabilizes the GC base pair toward electron capture as a transient anion. Energetically unstable diffuse states in the hydration shell are suggested to provide an intermediate state for the excess electron before molecular reorganization of the water molecules and the base pair results in a stable anion formation. The singly occupied molecular orbital (SOMO) in the anion radical complexes clearly shows that an excess electron localizes into a pi orbital of cytosine. The zero-point-energy (ZPE-) corrected adiabatic electron affinities (AEAs) of the GC-6H2O and GC-11H2O complexes, at the B3LYP/6-31+G** level of theory, were found to be 0.74 and 0.95 eV, respectively. However, the incorporation of bulk water as a solvent using the polarized continuum model (PCM) increases the EAs of these complexes to 1.77 eV.
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Affiliation(s)
- Anil Kumar
- Department of Chemistry, Oakland University, Rochester, Michigan 48309, USA
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21
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Radiation Effects On DNA: Theoretical Investigations Of Electron, Hole And Excitation Pathways To DNA Damage. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/978-1-4020-8184-2_20] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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22
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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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23
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Eustis S, Wang D, Lyapustina S, Bowen KH. Photoelectron spectroscopy of hydrated adenine anions. J Chem Phys 2007; 127:224309. [DOI: 10.1063/1.2806033] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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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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25
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Li X, Bowen KH, Haranczyk M, Bachorz RA, Mazurkiewicz K, Rak J, Gutowski M. Photoelectron spectroscopy of adiabatically bound valence anions of rare tautomers of the nucleic acid bases. J Chem Phys 2007; 127:174309. [DOI: 10.1063/1.2795719] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Stokes ST, Li X, Grubisic A, Ko YJ, Bowen KH. Intrinsic electrophilic properties of nucleosides: Photoelectron spectroscopy of their parent anions. J Chem Phys 2007; 127:084321. [PMID: 17764262 DOI: 10.1063/1.2774985] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The nucleoside parent anions 2(')-deoxythymidine(-), 2(')-deoxycytidine(-), 2(')-deoxyadenosine(-), uridine(-), cytidine(-), adenosine(-), and guanosine(-) were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG(-), the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.
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Affiliation(s)
- Sarah T Stokes
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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Kamiya M, Hirata S. Higher-order equation-of-motion coupled-cluster methods for electron attachment. J Chem Phys 2007; 126:134112. [PMID: 17430021 DOI: 10.1063/1.2715575] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
High-order equation-of-motion coupled-cluster methods for electron attachment (EA-EOM-CC) have been implemented with the aid of the symbolic algebra program TCE into parallel computer programs. Two types of size-extensive truncation have been applied to the electron-attachment and cluster excitation operators: (1) the electron-attachment operator truncated after the 2p-1h, 3p-2h, or 4p-3h level in combination with the cluster excitation operator after doubles, triples, or quadruples, respectively, defining EA-EOM-CCSD, EA-EOM-CCSDT, or EA-EOM-CCSDTQ; (2) the combination of up to the 3p-2h electron-attachment operator and up to the double cluster excitation operator [EA-EOM-CCSD(3p-2h)] or up to 4p-3h and triples [EA-EOM-CCSDT(4p-3h)]. These methods, capable of handling electron attachment to open-shell molecules, have been applied to the electron affinities of NH and C2, the excitation energies of CH, and the spectroscopic constants of all these molecules with the errors due to basis sets of finite sizes removed by extrapolation. The differences in the electron affinities or excitation energies between EA-EOM-CCSD and experiment are frequently in excess of 2 eV for these molecules, which have severe multideterminant wave functions. Including higher-order operators, the EA-EOM-CC methods predict these quantities accurate to within 0.01 eV of experimental values. In particular, the 3p-2h electron-attachment and triple cluster excitation operators are significant for achieving this accuracy.
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Affiliation(s)
- Muneaki Kamiya
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, Florida 32611-8435, USA
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28
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Mazurkiewicz K, Harańczyk M, Gutowski M, Rak J, Radisic D, Eustis SN, Wang D, Bowen KH. Valence Anions in Complexes of Adenine and 9-Methyladenine with Formic Acid: Stabilization by Intermolecular Proton Transfer. J Am Chem Soc 2007; 129:1216-24. [PMID: 17263404 DOI: 10.1021/ja066229h] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Photoelectron spectra of adenine-formic acid (AFA(-)) and 9-methyladenine-formic acid (MAFA(-)) anionic complexes have been recorded with 2.540 eV photons. These spectra reveal broad features with maxima at 1.5-1.4 eV that indicate formation of stable valence anions in the gas phase. The neutral and anionic complexes of adenine/9-methyladenine and formic acid were also studied computationally at the B3LYP, second-order Møller-Plesset, and coupled-cluster levels of theory with the 6-31++G** and aug-cc-pVDZ basis sets. The neutral complexes form cyclic hydrogen bonds, and the most stable dimers are bound by 17.7 and 16.0 kcal/mol for AFA and MAFA, respectively. The theoretical results indicate that the excess electron in both AFA(-) and MAFA(-) occupies a pi* orbital localized on adenine/9-methyladenine, and the adiabatic stability of the most stable anions amounts to 0.67 and 0.54 eV for AFA(-) and MAFA(-), respectively. The attachment of the excess electron to the complexes induces a barrier-free proton transfer (BFPT) from the carboxylic group of formic acid to a N atom of adenine or 9-methyladenine. As a result, the most stable structures of the anionic complexes can be characterized as neutral radicals of hydrogenated adenine (9-methyladenine) solvated by a deprotonated formic acid. The BFPT to the N atoms of adenine may be biologically relevant because some of these sites are not involved in the Watson-Crick pairing scheme and are easily accessible in the cellular environment. We suggest that valence anions of purines might be as important as those of pyrimidines in the process of DNA damage by low-energy electrons.
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Affiliation(s)
- Kamil Mazurkiewicz
- Department of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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Jalbout AF, Adamowicz L. Electron Attachment to DNA Base Complexes. ADVANCES IN QUANTUM CHEMISTRY 2007. [DOI: 10.1016/s0065-3276(06)52010-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
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30
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Tureček F. Computational Studies of Radicals Relevant to Nucleic Acid Damage. ADVANCES IN QUANTUM CHEMISTRY 2007. [DOI: 10.1016/s0065-3276(06)52005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
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31
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Mazurkiewicz K, Bachorz RA, Gutowski M, Rak J. On the Unusual Stability of Valence Anions of Thymine Based on Very Rare Tautomers: A Computational Study. J Phys Chem B 2006; 110:24696-707. [PMID: 17134233 DOI: 10.1021/jp065666f] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We characterized anionic states of thymine using various electronic structure methods, with the most accurate results obtained at the CCSD(T)/aug-cc-pVDZ level of theory followed by extrapolations to complete basis set limits. We found that the most stable anion in the gas phase is related to an imino-oxo tautomer, in which the N1H proton is transferred to the C5 atom. This valence anion, aT(c5)(nl), is characterized by an electron vertical detachment energy (VDE) of 1251 meV and it is adiabatically stable with respect to the canonical neutral nT(can) by 2.4 kcal/mol. It is also more stable than the dipole-bound (aT(dbs)(can)), and valence anion aT(val)(can) of the canonical tautomer. The VDE values for aT(dbs)(can)and T(val)(can) are 55 and 457 meV, respectively. Another, anionic, low-lying imino-oxo tautomer with a VDE of 2458 meV has a proton transferred from N3H to C5 aT(c5)(n3). It is less stable than aT(val)(can) by 3.3 kcal/mol. The mechanism of formation of anionic tautomers with the carbons C5 or C6 protonated may involve intermolecular proton transfer or dissociative electron attachment to the canonical neutral tautomer followed by a barrier-free attachment of a hydrogen atom to C5. The six-member ring structure of the anionic tautomers with carbon atoms protonated is unstable upon an excess electron detachment. Within the PCM hydration model, the low-lying valence anions become adiabatically bound with respect to the canonical neutral; becomes the most stable, being followed by aT(c5)(nl), aT(c5)(n3), aT(can), and aT(c5)(nl).
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Affiliation(s)
- Kamil Mazurkiewicz
- Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, 80-952 Gdańsk, Poland
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Frigato T, Svozil D, Jungwirth P. Valence- and Dipole-Bound Anions of the Thymine−Water Complex: Ab Initio Characterization of the Potential Energy Surfaces. J Phys Chem A 2005; 110:2916-23. [PMID: 16509613 DOI: 10.1021/jp054090b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The potential energy surfaces of the neutral and anionic thymine-water complexes are investigated using high-level ab initio calculations. Both dipole-bound (DB) and valence-bound (VB) anionic forms are considered. Four minima and three first-order stationary points are located, and binding energies are computed. All minima, for both anions, are found to be vertically and adiabatically stable. The binding energies are much higher for valence-bound than for dipole-bound anions. Adiabatic electron affinities are in the 66-287 meV range for VB anions and the 4-60 meV range for DB anions, and vertical detachment energies are in the 698-977 meV and 10-70 meV range for VB and DB anions, respectively. For cases where literature data are available, the computed values are in good agreement with previous experimental and theoretical studies. It is observed that electron attachment modifies the shape of the potential energy surfaces of the systems, especially for the valence-bound anions. Moreover, for both anions the size of the energy barrier between the two lowest energy minima is strongly reduced, rendering the coexistence of different structures more probable.
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Affiliation(s)
- Tomaso Frigato
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic
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