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Chen X, Karmaker N, Cloutier P, Bass AD, Zheng Y, Sanche L. Low-Energy Electron Damage to Plasmid DNA in Thin Films: Dependence on Substrates, Surface Density, Charging, Environment, and Uniformity. J Phys Chem B 2022; 126:5443-5457. [PMID: 35834372 DOI: 10.1021/acs.jpcb.2c03664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interaction of low-energy electrons (LEEs) with DNA plays a significant role in the mechanisms leading to biological damage induced by ionizing radiation, particularly in radiotherapy, and its sensitization by chemotherapeutic drugs and nanoparticles. Plasmids constitute the form of DNA found in mitochondria and appear as a suitable model of genomic DNA. In a search for the best LEE targets, damage was induced to plasmids, in thin films in vacuum, by 6, 10, and 100 eV electrons under single collision conditions. The yields of single- and double-strand breaks, other cluster damage, isolated base lesions, and crosslinks were measured by electrophoresis and enzyme treatment. The films were deposited on oriented graphite or polycrystalline tantalum, with or without DNA autoassembly via diaminopropane (Dap) intercalation. Yields were correlated with the influence of vacuum, film uniformity, surface density, substrates, and the DNA environment. Aided by surface potential measurements and scanning electron microscopy and atomic force microscopy images, the lyophilized Dap-DNA films were found to be the most practical high-quality targets. These studies pave the way to the fabrication of LEE target-films composed of plasmids intercalated with biomolecules that could mimic the cellular environment; for example, as a first step, by replacing Dap with an amino acid.
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Affiliation(s)
- Xingju Chen
- State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350116, P. R. China
| | - Nanda Karmaker
- Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Pierre Cloutier
- Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Andrew D Bass
- Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Yi Zheng
- State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350116, P. R. China.,Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Léon Sanche
- Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
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Liu W, Tan Z, Zhang L, Champion C. Investigation on the correlation between energy deposition and clustered DNA damage induced by low-energy electrons. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2018; 57:179-187. [PMID: 29335772 DOI: 10.1007/s00411-018-0730-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 01/10/2018] [Indexed: 06/07/2023]
Abstract
This study presents the correlation between energy deposition and clustered DNA damage, based on a Monte Carlo simulation of the spectrum of direct DNA damage induced by low-energy electrons including the dissociative electron attachment. Clustered DNA damage is classified as simple and complex in terms of the combination of single-strand breaks (SSBs) or double-strand breaks (DSBs) and adjacent base damage (BD). The results show that the energy depositions associated with about 90% of total clustered DNA damage are below 150 eV. The simple clustered DNA damage, which is constituted of the combination of SSBs and adjacent BD, is dominant, accounting for 90% of all clustered DNA damage, and the spectra of the energy depositions correlating with them are similar for different primary energies. One type of simple clustered DNA damage is the combination of a SSB and 1-5 BD, which is denoted as SSB + BD. The average contribution of SSB + BD to total simple clustered DNA damage reaches up to about 84% for the considered primary energies. In all forms of SSB + BD, the SSB + BD including only one base damage is dominant (above 80%). In addition, for the considered primary energies, there is no obvious difference between the average energy depositions for a fixed complexity of SSB + BD determined by the number of base damage, but average energy depositions increase with the complexity of SSB + BD. In the complex clustered DNA damage constituted by the combination of DSBs and BD around them, a relatively simple type is a DSB combining adjacent BD, marked as DSB + BD, and it is of substantial contribution (on average up to about 82%). The spectrum of DSB + BD is given mainly by the DSB in combination with different numbers of base damage, from 1 to 5. For the considered primary energies, the DSB combined with only one base damage contributes about 83% of total DSB + BD, and the average energy deposition is about 106 eV. However, the energy deposition increases with the complexity of clustered DNA damage, and therefore, the clustered DNA damage with high complexity still needs to be considered in the study of radiation biological effects, in spite of their small contributions to all clustered DNA damage.
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Affiliation(s)
- Wei Liu
- School of Electrical Engineering, Shandong University, Jinan, 250061, Shandong, People's Republic of China
- School of Information Science and Electrical Engineering, Shandong Jiaotong University, Jinan, 250357, People's Republic of China
| | - Zhenyu Tan
- School of Electrical Engineering, Shandong University, Jinan, 250061, Shandong, People's Republic of China.
| | - Liming Zhang
- Electric Power Research Institute of Tianjin Electric Power Corporation, Tianjin, 300384, People's Republic of China
| | - Christophe Champion
- Centre d'Etudes Nucléaires de Bordeaux Gradignan, Université de Bordeaux, CNRS/IN2P3, BP 120, 33175, Gradignan, France
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Ribar A, Huber SE, Smiałek MA, Tanzer K, Neustetter M, Schürmann R, Bald I, Denifl S. Hydroperoxyl radical and formic acid formation from common DNA stabilizers upon low energy electron attachment. Phys Chem Chem Phys 2018; 20:5578-5585. [PMID: 29410988 DOI: 10.1039/c7cp07697e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
2-Amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) and ethylenediaminetetraacetic acid (EDTA) are key components of biological buffers and are frequently used as DNA stabilizers in irradiation studies. Such surface or liquid phase studies are done with the aim to understand the fundamental mechanisms of DNA radiation damage and to improve cancer radiotherapy. When ionizing radiation is used, abundant secondary electrons are formed during the irradiation process, which are able to attach to the molecular compounds present on the surface. In the present study we experimentally investigate low energy electron attachment to TRIS and methyliminodiacetic acid (MIDA), an analogue of EDTA, supported by quantum chemical calculations. The most prominent dissociation channel for TRIS is through hydroperoxyl radical formation, whereas the dissociation of MIDA results in the formation of formic and acetic acid. These compounds are well-known to cause DNA modifications, like strand breaks. The present results indicate that buffer compounds may not have an exclusive protecting effect on DNA as suggested previously.
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Affiliation(s)
- Anita Ribar
- Institute for Ion Physics and Applied Physics and Center of Molecular Biosciences Innsbruck, Leopold Franzens University of Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.
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4
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Chen W, Chen S, Dong Y, Cloutier P, Zheng Y, Sanche L. Absolute cross-sections for DNA strand breaks and crosslinks induced by low energy electrons. Phys Chem Chem Phys 2018; 18:32762-32771. [PMID: 27878170 DOI: 10.1039/c6cp05201k] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Absolute cross sections (CSs) for the interaction of low energy electrons with condensed macromolecules are essential parameters to accurately model ionizing radiation induced reactions. To determine CSs for various conformational DNA damage induced by 2-20 eV electrons, we investigated the influence of the attenuation length (AL) and penetration factor (f) using a mathematical model. Solid films of supercoiled plasmid DNA with thicknesses of 10, 15 and 20 nm were irradiated with 4.6, 5.6, 9.6 and 14.6 eV electrons. DNA conformational changes were quantified by gel electrophoresis, and the respective yields were extrapolated from exposure-response curves. The absolute CS, AL and f values were generated by applying the model developed by Rezaee et al. The values of AL were found to lie between 11 and 16 nm with the maximum at 14.6 eV. The absolute CSs for the loss of the supercoiled (LS) configuration and production of crosslinks (CL), single strand breaks (SSB) and double strand breaks (DSB) induced by 4.6, 5.6, 9.6 and 14.6 eV electrons are obtained. The CSs for SSB are smaller, but similar to those for LS, indicating that SSB are the main conformational damage. The CSs for DSB and CL are about one order of magnitude smaller than those of LS and SSB. The value of f is found to be independent of electron energy, which allows extending the absolute CSs for these types of damage within the range 2-20 eV, from previous measurements of effective CSs. When comparison is possible, the absolute CSs are found to be in good agreement with those obtained from previous similar studies with double-stranded DNA. The high values of the absolute CSs of 4.6 and 9.6 eV provide quantitative evidence for the high efficiency of low energy electrons to induce DNA damage via the formation of transient anions.
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Affiliation(s)
- Wenzhuang Chen
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China.
| | - Shiliang Chen
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China.
| | - Yanfang Dong
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China.
| | - Pierre Cloutier
- Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Yi Zheng
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China.
| | - Léon Sanche
- Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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Liu W, Tan Z, Zhang L, Champion C. Calculation on spectrum of direct DNA damage induced by low-energy electrons including dissociative electron attachment. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2017; 56:99-110. [PMID: 28185000 DOI: 10.1007/s00411-016-0681-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2015] [Accepted: 12/30/2016] [Indexed: 06/06/2023]
Abstract
In this work, direct DNA damage induced by low-energy electrons (sub-keV) is simulated using a Monte Carlo method. The characteristics of the present simulation are to consider the new mechanism of DNA damage due to dissociative electron attachment (DEA) and to allow determining damage to specific bases (i.e., adenine, thymine, guanine, or cytosine). The electron track structure in liquid water is generated, based on the dielectric response model for describing electron inelastic scattering and on a free-parameter theoretical model and the NIST database for calculating electron elastic scattering. Ionization cross sections of DNA bases are used to generate base radicals, and available DEA cross sections of DNA components are applied for determining DNA-strand breaks and base damage induced by sub-ionization electrons. The electron elastic scattering from DNA components is simulated using cross sections from different theoretical calculations. The resulting yields of various strand breaks and base damage in cellular environment are given. Especially, the contributions of sub-ionization electrons to various strand breaks and base damage are quantitatively presented, and the correlation between complex clustered DNA damage and the corresponding damaged bases is explored. This work shows that the contribution of sub-ionization electrons to strand breaks is substantial, up to about 40-70%, and this contribution is mainly focused on single-strand break. In addition, the base damage induced by sub-ionization electrons contributes to about 20-40% of the total base damage, and there is an evident correlation between single-strand break and damaged base pair A-T.
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Affiliation(s)
- Wei Liu
- School of Electrical Engineering, Shandong University, Jinan, 250061, Shandong, People's Republic of China
| | - Zhenyu Tan
- School of Electrical Engineering, Shandong University, Jinan, 250061, Shandong, People's Republic of China.
| | - Liming Zhang
- School of Electrical Engineering, Shandong University, Jinan, 250061, Shandong, People's Republic of China
- Electric Power Research Institute of Tianjin Electric Power Corporation, Tianjin, 300384, People's Republic of China
| | - Christophe Champion
- Centre d'Etudes Nucléaires de Bordeaux Gradignan, Université de Bordeaux, CNRS/IN2P3, BP 120, 33175, Gradignan, France
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Choofong S, Cloutier P, Sanche L, Wagner JR. Base Release and Modification in Solid-Phase DNA Exposed to Low-Energy Electrons. Radiat Res 2016; 186:520-530. [PMID: 27802110 DOI: 10.1667/rr14476.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Ionization generates a large number of secondary low-energy electrons (LEEs) with a most probable energy of approximately 10 eV, which can break DNA bonds by dissociative electron attachment (DEA) and lead to DNA damage. In this study, we investigated radiation damage to dry DNA induced by X rays (1.5 keV) alone on a glass substrate or X rays combined with extra LEEs (average energy of 5.8 eV) emitted from a tantalum (Ta) substrate under an atmosphere of N2 and standard ambient conditions of temperature and pressure. The targets included calf-thymus DNA and double-stranded synthetic oligonucleotides. We developed analytical methods to measure the release of non-modified DNA bases from DNA and the formation of several base modifications by LC-MS/MS with isotopic dilution for precise quantification. The results show that the yield of non-modified bases as well as base modifications increase by 20-30% when DNA is deposited on a Ta substrate compared to that on a glass substrate. The order of base release (Gua > Ade > Thy ∼ Cyt) agrees well with several theoretical studies indicating that Gua is the most susceptible site toward sugar-phosphate cleavage. The formation of DNA damage by LEEs is explained by DEA leading to the release of non-modified bases involving the initial cleavage of N1-C1', C3'-O3' or C5'-O5' bonds. The yield of base modifications was lower than the release of non-modified bases. The main LEE-induced base modifications include 5,6-dihydrothymine (5,6-dHT), 5,6-dihydrouracil (5-dHU), 5-hydroxymethyluracil (5-HmU) and 5-formyluracil (5-ForU). The formation of base modifications by LEEs can be explained by DEA and cleavage of the C-H bond of the methyl group of Thy (giving 5-HmU and 5-ForU) and by secondary reactions of H atoms and hydride anions that are generated by primary LEE reactions followed by subsequent reaction with Cyt and Thy (giving 5,6-dHU and 5,6-dHT).
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Affiliation(s)
- Surakarn Choofong
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Pierre Cloutier
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Léon Sanche
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
| | - J Richard Wagner
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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7
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Butchosa C, Simon S, Blancafort L, Voityuk AA. On the performance of the Kohn–Sham orbital approach in the calculation of electron transfer parameters. The three state model. Phys Chem Chem Phys 2014; 16:17154-62. [DOI: 10.1039/c4cp02117g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The electron transfer parameters for the 3-state G⋯Ind system can be obtained using an efficient Kohn–Sham orbital based scheme.
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Affiliation(s)
- C. Butchosa
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química
- Universitat de Girona
- 17071 Girona, Spain
- Department of Chemistry
- University College London
| | - S. Simon
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química
- Universitat de Girona
- 17071 Girona, Spain
| | - L. Blancafort
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química
- Universitat de Girona
- 17071 Girona, Spain
| | - A. A. Voityuk
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química
- Universitat de Girona
- 17071 Girona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA)
- Barcelona, Spain
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8
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Massey S, Bass AD, Sanche L. Note: Transient negative ions as initiators of oxygen fixation in <20 eV electron-irradiated DNA. J Chem Phys 2013; 139:186101. [DOI: 10.1063/1.4829770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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9
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Boulanouar O, Fromm M, Mavon C, Cloutier P, Sanche L. Dissociative electron attachment to DNA-diamine thin films: impact of the DNA close environment on the OH- and O- decay channels. J Chem Phys 2013; 139:055101. [PMID: 23927286 PMCID: PMC3813476 DOI: 10.1063/1.4815967] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We measure the desorption of anions stimulated by the impact of 0-20 eV electrons on highly uniform thin films of plasmid DNA-diaminopropane. The results are accurately correlated with film thickness and composition by AFM and XPS measurements, respectively. Resonant structures in the H(-), O(-), and OH(-) yield functions are attributed to the decay of transient anions into the dissociative electron attachment (DEA) channel. The diamine induces ammonium-phosphate bridges along the DNA backbone, which suppresses the DEA O(-) channel and in counter-part increases considerably the desorption of OH(-). The close environment of the phosphate groups may therefore play an important role in modulating the rate and type of DNA damages induced by low energy electrons.
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Affiliation(s)
- Omar Boulanouar
- UMR CNRS 6249 Chrono-Environnement, Laboratoire de Chimie Physique et Rayonnements – Alain Chambaudet, LRC CEA, Université de Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France
| | - Michel Fromm
- UMR CNRS 6249 Chrono-Environnement, Laboratoire de Chimie Physique et Rayonnements – Alain Chambaudet, LRC CEA, Université de Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France
| | - Christophe Mavon
- UMR CNRS 6249 Chrono-Environnement, Laboratoire de Chimie Physique et Rayonnements – Alain Chambaudet, LRC CEA, Université de Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France
| | - Pierre Cloutier
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Québec J1H 5N4, Canada
| | - Léon Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Québec J1H 5N4, Canada
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10
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Correction for Meesat et al., Cancer radiotherapy based on femtosecond IR laser-beam filamentation yielding ultra-high dose rates and zero entrance dose. Proc Natl Acad Sci U S A 2013. [DOI: 10.1073/pnas.1301033110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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11
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Rezaee M, Cloutier P, Bass AD, Michaud M, Hunting DJ, Sanche L. Absolute cross section for low-energy-electron damage to condensed macromolecules: a case study of DNA. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:031913. [PMID: 23030950 PMCID: PMC3815646 DOI: 10.1103/physreve.86.031913] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/24/2012] [Indexed: 06/01/2023]
Abstract
Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions.
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Affiliation(s)
- Mohammad Rezaee
- Groupe en Sciences des Radiations, Départment de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
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Alizadeh E, Sanche L. Absolute measurements of radiation damage in nanometer-thick films. RADIATION PROTECTION DOSIMETRY 2012; 151:591-9. [PMID: 22562941 PMCID: PMC3846537 DOI: 10.1093/rpd/ncs036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The problem of absolute measurements of radiation damage in films of nanometer thicknesses is addressed. Thin films of DNA (∼2-160 nm) are deposited onto glass substrates and irradiated with varying doses of 1.5-keV X-rays under dry N(2) at atmospheric pressure and room temperature. For each different thickness, the damage is assessed by measuring the loss of the supercoiled configuration as a function of incident photon fluence. From the exposure curves, the G-values are deduced, assuming that X-ray photons interacting with DNA deposit all of their energy in the film. The results show that the G-value (i.e. damage per unit of deposited energy) increases with film thickness and reaches a plateau at 30±5 nm. This thickness dependence provides a correction factor to estimate the actual G-value for films with thicknesses <30 nm thickness. Thus, the absolute values of the damage can be compared with that of films of any thickness under different experimental conditions.
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Affiliation(s)
- Elahe Alizadeh
- Groupe en Science des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la santé, Université de Sherbrooke, Sherbrooke, Canada J1H 5N4.
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13
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Kumar SVK, Pota T, Peri D, Dongre AD, Rao BJ. Low energy electron induced damage to plasmid DNA pQE30. J Chem Phys 2012; 137:045101. [DOI: 10.1063/1.4737182] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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14
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Butchosa C, Simon S, Blancafort L, Voityuk A. MS-CASPT2 Study of Hole Transfer in Guanine–Indole Complexes Using the Generalized Mulliken–Hush Method: Effective Two-State Treatment. J Phys Chem B 2012; 116:7815-20. [DOI: 10.1021/jp303675h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. Butchosa
- Institut de Química Computacional,
Departament de Química, Universitat de Girona, Campus de Montilivi, Girona, 17071 Spain
| | - S. Simon
- Institut de Química Computacional,
Departament de Química, Universitat de Girona, Campus de Montilivi, Girona, 17071 Spain
| | - L. Blancafort
- Institut de Química Computacional,
Departament de Química, Universitat de Girona, Campus de Montilivi, Girona, 17071 Spain
| | - A. Voityuk
- Institut de Química Computacional,
Departament de Química, Universitat de Girona, Campus de Montilivi, Girona, 17071 Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, 08010 Spain
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15
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Alizadeh E, Sanche L. Precursors of solvated electrons in radiobiological physics and chemistry. Chem Rev 2012; 112:5578-602. [PMID: 22724633 DOI: 10.1021/cr300063r] [Citation(s) in RCA: 225] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elahe Alizadeh
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
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16
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Mirsaleh-Kohan N, Bass AD, Cloutier P, Massey S, Sanche L. Low energy electron stimulated desorption from DNA films dosed with oxygen. J Chem Phys 2012; 136:235104. [PMID: 22779623 PMCID: PMC3820536 DOI: 10.1063/1.4729781] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O(2). The OH(-) desorption yields increase markedly with exposure to O(2) at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O(-), attributable to dissociative electron attachment to trapped O(2) molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O(2) shows that this surprising increase in OH(-) desorption, at elevated temperatures, arises from the reaction of O(2) with damaged DNA sites. These results thus appear to be a manifestation of the so-called "oxygen fixation" effect, well known in radiobiology.
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Affiliation(s)
- Nasrin Mirsaleh-Kohan
- Groupe en sciences des radiations, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Alizadeh E, Sanche L. Induction of Strand Breaks in DNA films by Low Energy Electrons and Soft X-ray under Nitrous Oxide Atmosphere. Radiat Phys Chem Oxf Engl 1993 2012; 81:33-39. [PMID: 24976692 DOI: 10.1016/j.radphyschem.2011.09.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Five-monolayer (5ML) plasmid DNA films deposited on glass and tantalum substrates were exposed to Al Kα X-rays of 1.5 keV under gaseous nitrous oxide (N2O) at atmospheric pressure and temperature. Whereas the damage yields for DNA deposited on glass are due to soft X-rays, those arising from DNA on tantalum are due to both the interaction of low energy photoelectrons from the metal and X-rays. Then, the differences in the yields of damage on glass and tantalum substrates, essentially arises from interaction of essentially low-energy electrons (LEEs) with DNA molecules and the surrounding atmosphere. The G-values (i.e., the number of moles of product per Joule of energy absorbed) for DNA strand breaks induced by LEEs (GLEE) and the lower limit of G-values for soft X-ray photons (GXL) were calculated and the results compared to those from previous studies under atmospheric conditions and other ambient gases, such as N2 and O2. Under N2O, the G-values for loss of supercoiled DNA are 103±15 nmol/J for X-rays, and 737±110 nmol/J for LEEs. Compared to corresponding values in an O2 atmosphere, the effectiveness of X-rays to damage DNA in N2O is less, but the G value for LEEs in N2O is more than twice the corresponding value for an oxygenated environment. This result indicates a higher effectiveness for LEEs relative to N2 and O2 environments in causing SSB and DSB in an N2O environment. Thus, the previously observed radiosensitization of cells by N2O may not be only due to OH• radicals but also to the reaction of LEE with N2O molecules near DNA. The previous experiments with N2 and O2 and the present one demonstrate the possibility to investigate damage induced by LEEs to biomolecules under various type of surrounding atmospheres.
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Affiliation(s)
- Elahe Alizadeh
- Groupe en science des radiations, Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, J1H 5N4, Sherbrooke, Canada
| | - Léon Sanche
- Groupe en science des radiations, Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, J1H 5N4, Sherbrooke, Canada
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Alizadeh E, Sanche L. Measurements of G values for DNA damage induced by low-energy electrons. J Phys Chem B 2011; 115:14852-8. [PMID: 22035128 DOI: 10.1021/jp207922n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We address the problem of measuring G values (damage per unit of deposited energy) for low-energy electrons (LEEs) below 30 eV. Such values (G(LEE)) usually have to be derived from damage yields in nanometer- (~10-nm-) thick films, which are too thin to allow complete absorption of the energy of LEEs. In this work, we determine optimum corrections to obtain reliable G(LEE) values in 2-80-nm-thick films of plasmid DNA that are not uniform. G(LEE) was found to increase with average film thickness and reach a plateau at 260 ± 50 nmol/J around 20 nm, which corresponds to the most reliable value. The previously measured G(LEE) values for films thinner than 20 nm that were underestimated can be corrected using a factor derived from the present results. This method could be used to obtain reliable G(LEE) values for other biomolecules so as to enable the comparison of LEE-induced damage to that produced by other types of radiation under various experimental conditions.
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Affiliation(s)
- Elahe Alizadeh
- Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Canada.
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DNA-Platinum Thin Films for Use in Chemoradiation Therapy Studies. Bioinorg Chem Appl 2011; 2012:923914. [PMID: 21977010 PMCID: PMC3184495 DOI: 10.1155/2012/923914] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 08/03/2011] [Indexed: 11/17/2022] Open
Abstract
Dry films of platinum chemotherapeutic drugs covalently bound to plasmid DNA (Pt-DNA) represent a useful experimental model to investigate direct effects of radiation on DNA in close proximity to platinum chemotherapeutic agents, a situation of considerable relevance to understand the mechanisms underlying concomitant chemoradiation therapy. In the present paper we determine the optimum conditions for preparation of Pt-DNA films for use in irradiation experiments. Incubation conditions for DNA platination reactions have a substantial effect on the structure of Pt-DNA in the films. The quantity of Pt bound to DNA as a function of incubation time and temperature is measured by inductively coupled plasma mass spectroscopy. Our experiments indicate that chemical instability and damage to DNA in Pt-DNA samples increase when DNA platination occurs at 37°C for 24 hours, the condition which has been extensively used for in vitro studies. Platination of DNA for the formation of Pt-DNA films is optimal at room temperature for reaction times less than 2 hours. By increasing the concentration of Pt compounds relative to DNA and thus accelerating the rate of their mutual binding, it is possible to prepare Pt-DNA samples containing known concentrations of Pt while reducing DNA degradation caused by more lengthy procedures.
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Alizadeh E, Cloutier P, Hunting D, Sanche L. Soft X-ray and low energy electron-induced damage to DNA under N2 and O2 atmospheres. J Phys Chem B 2011; 115:4523-31. [PMID: 21452797 PMCID: PMC3846624 DOI: 10.1021/jp200947g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
DNA damage induced by low energy electrons (LEEs) and soft X-rays is measured under dry nitrogen and oxygen at atmospheric pressure and temperature. Five-monolayer plasmid DNA films deposited on tantalum and glass substrates are exposed to Al K(α) X-rays of 1.5 keV in the two different environments. From the damage yields for DNA, G values are extracted for X-rays and LEEs. The G values for LEEs are 3.5 and 3.4 higher than those for X-ray photons under N(2) and O(2) atmospheres, respectively. Because most of the measured damage is in the form of single strand breaks (SSB), this result indicates a much higher effectiveness for LEEs relative to X-rays in causing SSB in both environments. The results indicate that the oxygen fixation mechanism, which is highly effective in increasing radiobiological effectiveness, under aerobic conditions, is operative on the type of damage created at the early stage of DNA radiolysis by LEEs.
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Affiliation(s)
- Elahe Alizadeh
- Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada.
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Zheng Y, Sanche L. Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons. J Chem Phys 2010; 133:155102. [PMID: 20969428 PMCID: PMC3217039 DOI: 10.1063/1.3505046] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (∼4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons.
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Affiliation(s)
- Yi Zheng
- Research Institute of Photocatalysis, Fuzhou University, Fuzhou 35002, People's Republic of China.
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Ptasińska S, Li Z, Mason NJ, Sanche L. Damage to amino acid-nucleotide pairs induced by 1 eV electrons. Phys Chem Chem Phys 2010; 12:9367-72. [PMID: 20563347 PMCID: PMC3828173 DOI: 10.1039/b926267a] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have investigated the role of two selected amino acids, glycine and arginine, on damage induced to a short chain of single stranded DNA, the tetramer GCAT, during 1 eV electron exposure. At this energy, DNA has a high cross section for DNA damage via exclusively dissociative electron attachment. Surprisingly, at low ratios of glycine:GCAT, an increase in the total fragmentation yield is observed, whilst at higher ratios, glycine and arginine appear to protect DNA from the direct action of electrons. In addition, binding energies were calculated by molecular modelling of the interactions between these amino acids and either nucleobases or nucleotides. These binding energies appear to be related to the ability of amino acids to protect DNA against low energy electron damage.
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Affiliation(s)
- Sylwia Ptasińska
- Department of Physics & Astronomy, The Open University, Milton Keynes, UK MK7 6AA.
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Kopyra J, Abdoul-Carime H. Dissociation of gaseous zwitterion glycine-betaine by slow electrons. J Chem Phys 2010; 132:204302. [DOI: 10.1063/1.3436718] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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