1
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Milešević D, Stimson J, Popat D, Robertson P, Vallance C. Photodissociation dynamics of tetrahydrofuran at 193 nm. Phys Chem Chem Phys 2023; 25:25322-25330. [PMID: 37702573 DOI: 10.1039/d3cp01974h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
Tetrahydrofuran (THF), a cyclic ether with the chemical formula C4H8O, can be considered the simplest analog of the deoxyribose backbone component of deoxyribonucleic acid (DNA). As such, it provides a useful model for probing the photochemistry of such biomolecular motifs. We present a velocity-map imaging study into the ultraviolet dissociation of THF at a wavelength of 193 nm. Excitation to the S1 state occurs via a 3s ← n transition involving a lone-pair electron on the oxygen atom, and has been shown by other authors to result in rapid ring opening via cleavage of one of the C-O bonds to form a ring-opened C4H8O diradical, followed by C-C bond cleavage over a longer timescale to form either OCH2 + C3H6 products (Channel 1a), HOCH2 + C2H5 products (Channel 1b), or OCH2CH2 + C2H4 products (Channel 2). The C2H4O products formed via Channel 2 are unstable on the timescale of our experiment and dissociate further to form CH3 and CHO. We also observe a number of minor products resulting from H or H2 loss from the primary photofragments. The speed distributions observed for all photofragments are broad, indicating excitation of a range of rotational and vibrational states of the products. The angular distributions of the photofragments show an interesting speed dependence: the slowest products have almost isotropic angular distributions, but the magnitude of the recoil anisotropy increases monotonically with photofragment speed. The fastest products exhibit highly anisotropic angular distributions, with the recoil anisotropy parameter β approaching its limiting value of -1 (-0.75 for Channel 1 and -0.5 for Channel 2). This behaviour is attributed to the range of timescales over which the diradical intermediate dissociates into the observed photofragments. Rapid dissociation leads to fast photofragments which retain the correlation between the transition dipole moment for the S1 ← S0 excitation (which lies perpendicular to the ring) and the photofragment velocities (which lie predominantly in the plane of the ring). Slow dissociation results in a high degree of energy redistribution into internal modes, slower photofragments, and loss of correlation between the photofragment velocities and the transition dipole. The higher barrier associated with dissociation via Channel 2 suggests somewhat longer lifetimes for the diradical intermediate and is consistent with a corresponding reduction in the maximum observed value for β.
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Affiliation(s)
- Dennis Milešević
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK.
| | - Joseph Stimson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK.
| | - Divya Popat
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK.
| | - Patrick Robertson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK.
| | - Claire Vallance
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA, UK.
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2
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Repurposing Antimalarial Pyronaridine as a DNA Repair Inhibitor to Exploit the Full Potential of Gold-Nanoparticle-Mediated Radiation Response. Pharmaceutics 2022; 14:pharmaceutics14122795. [PMID: 36559288 PMCID: PMC9783290 DOI: 10.3390/pharmaceutics14122795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 12/01/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022] Open
Abstract
Radiation therapy (RT) is frequently used to locally treat tumors. One of the major issues in RT is normal tissue toxicity; thus, it is necessary to limit dose escalation for enhanced local control in patients that have locally advanced tumors. Integrating radiosensitizing agents such as gold nanoparticles (GNPs) into RT has been shown to greatly increase the cure rate of solid tumors. The objective of this study was to explore the repurposing of an antimalarial drug, pyronaridine (PYD), as a DNA repair inhibitor to further enhance RT/GNP-induced DNA damage in cancerous cell lines. We were able to achieve inhibitory effects of DNA repair due to PYD at 500 nM concentration. Our results show a significant enhancement in DNA double-strand breaks of 42% in HeLa cells treated with PYD/GNP/RT in comparison to GNP/RT alone when irradiated with a dose of 2 Gy. Furthermore, there was a significant reduction in cellular proliferation for both HeLa and HCT-116 irradiated cells with the combined treatment of PYD/GNP/RT. Therefore, the emergence of promising novel concepts introduced in this study could lay the foundation for the transition of this treatment modality into clinical environments.
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3
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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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4
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Ebel K, Bald I. Low-Energy (5-20 eV) Electron-Induced Single and Double Strand Breaks in Well-Defined DNA Sequences. J Phys Chem Lett 2022; 13:4871-4876. [PMID: 35617198 PMCID: PMC9189919 DOI: 10.1021/acs.jpclett.2c00684] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Ionizing radiation is used in cancer radiation therapy to effectively damage the DNA of tumors. The main damage is due to generation of highly reactive secondary species such as low-energy electrons (LEEs). The accurate quantification of DNA radiation damage of well-defined DNA target sequences in terms of absolute cross sections for LEE-induced DNA strand breaks is possible by the DNA origami technique; however, to date, it is possible only for DNA single strands. In the present work DNA double strand breaks in the DNA sequence 5'-d(CAC)4/5'-d(GTG)4 are compared with DNA single strand breaks in the oligonucleotides 5'-d(CAC)4 and 5'-d(GTG)4 upon irradiation with LEEs in the energy range from 5 to 20 eV. A maximum of strand break cross section was found around 7 and 10 eV independent of the DNA sequence, indicating that dissociative electron attachment is the underlying mechanism of strand breakage and confirming previous studies using plasmid DNA.
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5
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Lee Y, Yao X, Fischetti MV, Cho K. Real-time ab initio simulation of inelastic electron scattering using the exact, density functional, and alternative approaches. Phys Chem Chem Phys 2020; 22:8616-8624. [DOI: 10.1039/c9cp06376e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inelastic electron scattering phenomena in chemical/physical/materials interests: electron radiation damage in materials; DNA damaged by electron scattering; electron therapy; electron microscope; electron-beam-induced deposition for nanofabrication.
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Affiliation(s)
- Yeonghun Lee
- Department of Materials Science and Engineering
- University of Texas at Dallas
- Richardson
- USA
| | - Xiaolong Yao
- Department of Materials Science and Engineering
- University of Texas at Dallas
- Richardson
- USA
| | - Massimo V. Fischetti
- Department of Materials Science and Engineering
- University of Texas at Dallas
- Richardson
- USA
| | - Kyeongjae Cho
- Department of Materials Science and Engineering
- University of Texas at Dallas
- Richardson
- USA
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6
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Brodeur N, Cloutier P, Bass AD, Bertrand G, Hunting DJ, Grandbois M, Sanche L. Absolute cross section for DNA damage induced by low-energy (10 eV) electrons: Experimental refinements and sample characterization by AFM. J Chem Phys 2018; 149:164904. [PMID: 30384690 DOI: 10.1063/1.5041805] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
This work describes multiple experimental improvements for measuring absolute cross sections of DNA damage induced by low-energy electrons in nanometer-thick films in vacuum. Measurements of such cross sections are particularly sensitive to film thickness and uniformity. Using atomic force microscopy in 70% ethanol, we present a novel and effective method to determine plasmid DNA film thickness and uniformity that combines height histograms and force-distance curves. We also investigate film deposition with DNA intercalated with 1,3-diaminopropane (Dap) on tantalum-coated substrates as a convenient and cost-effective alternative to the previously-used graphite substrate. The tantalum substrate permits deposition of films very similar to those formed on graphite. Using these refinements and further optimizations of the experimental procedure, we measure an absolute cross section of (7.4 ± 2.3) × 10-18 cm2 per nucleotide for conformational damage to a 3197 base-pair plasmid, induced by 10 eV electrons, which we believe should be considered as a reference value.
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Affiliation(s)
- N Brodeur
- Department of Nuclear Medicine and Radiobiology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - P Cloutier
- Department of Nuclear Medicine and Radiobiology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - A D Bass
- Department of Nuclear Medicine and Radiobiology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - G Bertrand
- Department of Pharmacology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - D J Hunting
- Department of Nuclear Medicine and Radiobiology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - M Grandbois
- Department of Pharmacology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - L Sanche
- Department of Nuclear Medicine and Radiobiology, University of Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
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7
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Smith ME, Green NJB, Pimblott SM. Methods for the Simulation of the Slowing of Low-Energy Electrons in Water. J Comput Chem 2018; 39:2217-2225. [PMID: 30238486 DOI: 10.1002/jcc.25536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/29/2018] [Accepted: 06/29/2018] [Indexed: 11/08/2022]
Abstract
A computational Monte Carlo simulation approach for modeling the thermalization of low-energy electrons is presented. The simulation methods rely on, and use, experimentally based cross sections for elastic and inelastic collisions. To demonstrate the different simulation options, average numbers of interactions and the range of low-energy electrons with initial energies ranging from 1 to 20 eV are calculated for density normalized gaseous water. Experimental gas-phase cross sections for (subexcitation) electrons of energies in the range of 1-20 eV were taken from the compilation of Hayashi. The ballistic collision-by-collision simulations provide information on the intricacies of the thermalization processes not available experimentally. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Marisa E Smith
- Dalton Cumbrian Facility, West Lakes Science and Technology Park, Moor Row, CA24 3HA, United Kingdom.,School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - N J B Green
- Department of Physical & Theoretical Chemistry, Oxford University, Oxford, OX1 3PA, United Kingdom
| | - S M Pimblott
- Dalton Cumbrian Facility, West Lakes Science and Technology Park, Moor Row, CA24 3HA, United Kingdom.,School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.,Nuclear Science User Facilities, Idaho National Laboratory, Idaho Falls, Idaho, IDA3415
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8
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Aouina NY, Chaoui ZEA. Simulation of positron and electron elastic mean free path and diffusion angle on DNA nucleobases from 10 eV to 100 keV. SURF INTERFACE ANAL 2018. [DOI: 10.1002/sia.6510] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | - Zine-El-Abidine Chaoui
- Laboratory of Optoelectronic and Devices; University Ferhat Abbas Setif1; Algeria
- Physics Department, Faculty of Sciences; University of Setif1; Setif Algeria
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9
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de la Fuente Rosales L, Incerti S, Francis Z, Bernal MA. Accounting for radiation-induced indirect damage on DNA with the Geant 4-DNA code. Phys Med 2018; 51:108-116. [PMID: 29908994 DOI: 10.1016/j.ejmp.2018.06.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 06/05/2018] [Accepted: 06/06/2018] [Indexed: 01/02/2023] Open
Abstract
The use of Monte Carlo (MC) simulations remains a powerful tool to study the biological effects induced by ionizing radiation on living beings. Several MC codes are commonly used in research fields such as nanodosimetry, radiotherapy, radiation protection, and space radiation. This work presents an enhancement of an existing model [1] for radiobiological purposes, to account for the indirect DNA damage induced by ionizing particles. The Geant4-DNA simulation toolkit was used to simulate the physical, pre-chemical, and chemical stages of early DNA damage induced by protons and α-particles. Liquid water was used as the medium for simulations. Two phase-space files were generated, one containing the energy deposition events and another with the position of chemical species produced by water radiolysis from 0.1 ps up to 1 ns. These files were used as input in the radiobiological code that contains the genetic material model with atomic resolution, consisting of several copies of 30 nm chromatin fibers. The B-DNA configuration was used. This work focused on the indirect damage produced by the hydroxyl radical (OH) attack on the sugar-phosphate group. The approach followed to account for the indirect DNA damage was the same as those used by other radiobiological codes [2,3]. The critical parameter considered here was the reaction radius, which was calculated from the Smoluchowski's diffusion equation. Single, double, and total strand break yields produced by direct, indirect, and mixed mechanisms are reported. The obtained results are consistent with experimental and calculation data sets published in the literature.
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Affiliation(s)
| | | | - Ziad Francis
- Université Saint Joseph, Faculty of Sciences, Department of Physics, Beirut, Lebanon
| | - Mario A Bernal
- Departamento de Física Aplicada, Instituto de Física "Gleb Wataghin", UNICAMP, Campinas, Brazil
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10
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Colmenares R, Krupa K, Muñoz A, Blanco F, Williart A, García G. A process to describe radiation damage at the molecular level. Application to the 125I seeds in water. Appl Radiat Isot 2018; 140:163-170. [PMID: 30015047 DOI: 10.1016/j.apradiso.2018.05.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 05/29/2018] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
Abstract
The correlation between the absorbed energy and the induced biological damage still has unclear aspects, especially in the low energy and low dose rate irradiation regimes. From the knowledge of the molecular-induced effects (dissociations), it would be possible to better understand the side effects of radiation, such as induced cancers or damage to healthy tissue. With this in view, this paper presents results of a simulation of a 125I-seed treatment with an event-by-event MC code (LEPTS) specifically designed to account for the low energy secondary particle interactions, such as electron attachment, vibro-rotational and neutral dissociation interactions. This calculation allowed us to analyze the potential radiation damage not only in connection with the energy deposition, but also in terms of induced molecular dissociations by taking into account ionizing and non-ionizing dissociative processes. We propose that this description of the molecular level damage be the basis for nanodosimetric evaluations.
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Affiliation(s)
- R Colmenares
- Servicio de Radiofísica, Hospital Universitario Ramón y Cajal, Ctra Colmenar Viejo km 9.1, 28034 Madrid, Spain; Instituto de Física Fundamental (IFF), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain.
| | - K Krupa
- Instituto de Física Fundamental (IFF), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - A Muñoz
- Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Av. Complutense 22, 28040 Madrid, Spain
| | - F Blanco
- Departamento de Física Atómica, Molecular y Nuclear, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - A Williart
- Departamento de Física Interdisciplinar, Universidad Nacional de Educación a Distancia (UNED), Senda del Rey 9, 28040 Madrid, Spain
| | - G García
- Instituto de Física Fundamental (IFF), Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
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11
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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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12
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Thopan P, Yu L, Brown IG, Tippawan U. Low-Energy Ion-Species-Dependent Induction of DNA Double-Strand Breaks: Ion Energy and Fluence Thresholds. Radiat Res 2017; 188:426-432. [PMID: 28767313 DOI: 10.1667/rr14721.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The goal of this study was to determine the critical ion-radiation conditions under which heavy ion beams can induce DNA double-strand breaks. Helium, nitrogen and argon-ion beams in the energy range of 20 eV to 2 keV were used to irradiate naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. The topological forms of DNA were subsequently analyzed using gel electrophoresis. The DNA forms were changed from the original supercoiled to damaged relaxed and linear forms, depending on the ion mass, energy, fluence and inertia. We found ion energy and fluence thresholds above which direct double-strand breaks can occur. The threshold is discussed in terms of the areal ion-energy density and the cross-section.
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Affiliation(s)
- Prutchayawoot Thopan
- a Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Liangdeng Yu
- a Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.,b Thailand Center of Excellence in Physics, Commission on Higher Education, Bangkok 10400, Thailand
| | - Ian G Brown
- c Lawrence Berkeley National Laboratory, Berkeley, California 94720
| | - Udomrat Tippawan
- a Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
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13
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Rezaee M, Hill RP, Jaffray DA. The Exploitation of Low-Energy Electrons in Cancer Treatment. Radiat Res 2017; 188:123-143. [PMID: 28557630 DOI: 10.1667/rr14727.1] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Given the distinct characteristics of low-energy electrons (LEEs), particularly at energies less than 30 eV, they can be applied to a wide range of therapeutic modalities to improve cancer treatment. LEEs have been shown to efficiently produce complex molecular damage resulting in substantial cellular toxicities. Since LEEs are produced in copious amounts from high-energy radiation beam, including photons, protons and ions; the control of LEE distribution can potentially enhance the therapeutic radio of such beams. LEEs can play a substantial role in the synergistic effect between radiation and chemotherapy, particularly halogenated and platinum-based anticancer drugs. Radiosensitizing entities containing atoms of high atomic number such as gold nanoparticles can be a source of LEE production if high-energy radiation interacts with them. This can provide a high local density of LEEs in a cell and produce cellular toxicity. Auger-electron-emitting radionuclides also create a high number of LEEs in each decay, which can induce lethal damage in a cell. Exploitation of LEEs in cancer treatment, however, faces a few challenges, such as dosimetry of LEEs and selective delivery of radiosensitizing and chemotherapeutic molecules close to cellular targets. This review first discusses the rationale for utilizing LEEs in cancer treatment by explaining their mechanism of action, describes theoretical and experimental studies at the molecular and cellular levels, then discusses strategies for achieving modification of the distribution and effectiveness of LEEs in cancerous tissue and their associated clinical benefit.
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Affiliation(s)
- Mohammad Rezaee
- Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Ontario Cancer Institute and Campbell Family Institute for Cancer Research and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - Richard P Hill
- Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Ontario Cancer Institute and Campbell Family Institute for Cancer Research and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
| | - David A Jaffray
- Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Ontario Cancer Institute and Campbell Family Institute for Cancer Research and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada
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14
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Fromm M, Boulanouar O. Low energy electrons and ultra-soft X-rays irradiation of plasmid DNA. Technical innovations. Radiat Phys Chem Oxf Engl 1993 2016. [DOI: 10.1016/j.radphyschem.2016.05.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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15
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Spaas C, Dok R, Deschaume O, De Roo B, Vervaele M, Seo JW, Bartic C, Hoet P, Van den Heuvel F, Nuyts S, Locquet JP. Dependence of Gold Nanoparticle Radiosensitization on Functionalizing Layer Thickness. Radiat Res 2016; 185:384-92. [PMID: 26950059 DOI: 10.1667/rr14207.1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Gold nanoparticles functionalized with polyethylene glycol of different chain lengths are used to determine the influence of the capping layer thickness on the radiosensitizing effect of the particles. The size variations in organic coating, built up with polyethylene glycol polymers of molecular weight 1-20 kDa, allow an evaluation of the decrease in dose enhancement percentages caused by the gold nanoparticles at different radial distances from their surface. With localized eradication of malignant cells as a primary focus, radiosensitization is most effective after internalization in the nucleus. For this reason, we performed controlled radiation experiments, with doses up to 20 Gy and particle diameters in a range of 5-30 nm, and studied the relaxation pattern of supercoiled DNA. Subsequent gel electrophoresis of the suspensions was performed to evaluate the molecular damage and consecutively quantify the gold nanoparticle sensitization. In conclusion, on average up to 58.4% of the radiosensitizing efficiency was lost when the radial dimensions of the functionalizing layer were increased from 4.1 to 15.3 nm. These results serve as an experimental supplement for biophysical simulations and demonstrate the influence of an important parameter in the development of nanomaterials for targeted therapies in cancer radiotherapy.
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Affiliation(s)
| | | | | | | | | | | | | | - Peter Hoet
- d Public Health and Primary Care, Environment and Health, Katholieke Universiteit Leuven, Belgium; and
| | - Frank Van den Heuvel
- b Oncology.,e CRUK/MRC Institute for Radiation Oncology and Biology, University of Oxford, Oxford OX3 7DQ, United Kingdom
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16
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Chen B, Zhou L. Computational study on mechanisms of the anticancer drug: Cisplatin and novel polynuclear platinum(II) interaction with sulfur-donor biomolecules and DNA purine bases. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2015.09.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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17
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Interference effects in the electron and positron scattering from molecules at intermediate and high energies. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.06.066] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Sato K, Nishikino M, Kawachi T, Shimokawa T, Imai T, Teshima T, Nishimura H, Kando M. A laser-plasma-produced soft X-ray laser at 89 eV generates DNA double-strand breaks in human cancer cells. JOURNAL OF RADIATION RESEARCH 2015; 56:633-638. [PMID: 25862698 PMCID: PMC4497388 DOI: 10.1093/jrr/rrv015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 01/28/2015] [Accepted: 03/06/2015] [Indexed: 06/04/2023]
Abstract
While it has been expected that X-ray laser will be widely applied to biomedical studies, this has not been achieved to date and its biological effects such as DNA damage have not been evaluated. As a first step for its biological application, we developed a culture cell irradiation system, particularly designed for a plasma-driven soft X-ray laser pulse, to investigate whether the soft X-ray laser is able to induce DNA double strand breaks (DSBs) in living cells or not. The human adenocarcimona cell line A549 was irradiated with the soft X-ray laser at a photon energy of 89 eV and the repair focus formation of the DSBs was assessed by immunofluorescence staining with antiphosphorylated DNA-PKcs (p-DNA-PKcs), ATM (p-ATM) and γ-H2AX antibody. The p-DNA-PKcs, ATM, and γ-H2AX foci were clearly identified after soft X-ray laser irradiation. Furthermore, the increase in the X-ray laser shot number, even from a single shot, results in the increase in p-DNA-PKcs foci. These results are the first evidence that the 89 eV soft X-ray laser is able to induce DSB in living cells. Our study demonstrated that this irradiation system is a useful tool for investigating the radiobiological effect of soft X-ray laser.
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Affiliation(s)
- Katsutoshi Sato
- Cancer Metastasis Research Team, Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Masaharu Nishikino
- X-ray Laser Application Group, Quantum Beam Science Directorate, Kansai Photon Science Institute, Japan Atonic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto, 619-0215, Japan
| | - Tetsuya Kawachi
- X-ray Laser Application Group, Quantum Beam Science Directorate, Kansai Photon Science Institute, Japan Atonic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto, 619-0215, Japan
| | - Takashi Shimokawa
- Cancer Metastasis Research Team, Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Takashi Imai
- Advanced Radiation Biology Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Teruki Teshima
- Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3 Nakamichi, Higashinari-ku, Osaka, 537-8511 Japan
| | - Hiroaki Nishimura
- Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Masaki Kando
- Laser Electron Accelerator Group, Quantum Beam Science Directorate, Kansai Photon Science Institute, Japan Atonic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto, 619-0215, Japan
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19
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Sequence dependence of electron-induced DNA strand breakage revealed by DNA nanoarrays. Sci Rep 2014; 4:7391. [PMID: 25487346 PMCID: PMC4260214 DOI: 10.1038/srep07391] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 11/20/2014] [Indexed: 01/18/2023] Open
Abstract
The electronic structure of DNA is determined by its nucleotide sequence, which is for instance exploited in molecular electronics. Here we demonstrate that also the DNA strand breakage induced by low-energy electrons (18 eV) depends on the nucleotide sequence. To determine the absolute cross sections for electron induced single strand breaks in specific 13 mer oligonucleotides we used atomic force microscopy analysis of DNA origami based DNA nanoarrays. We investigated the DNA sequences 5′-TT(XYX)3TT with X = A, G, C and Y = T, BrU 5-bromouracil and found absolute strand break cross sections between 2.66 · 10−14 cm2 and 7.06 · 10−14 cm2. The highest cross section was found for 5′-TT(ATA)3TT and 5′-TT(ABrUA)3TT, respectively. BrU is a radiosensitizer, which was discussed to be used in cancer radiation therapy. The replacement of T by BrU into the investigated DNA sequences leads to a slight increase of the absolute strand break cross sections resulting in sequence-dependent enhancement factors between 1.14 and 1.66. Nevertheless, the variation of strand break cross sections due to the specific nucleotide sequence is considerably higher. Thus, the present results suggest the development of targeted radiosensitizers for cancer radiation therapy.
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20
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Kouass Sahbani S, Sanche L, Cloutier P, Bass AD, Hunting DJ. Loss of cellular transformation efficiency induced by DNA irradiation with low-energy (10 eV) electrons. J Phys Chem B 2014; 118:13123-31. [PMID: 25325149 DOI: 10.1021/jp508170c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Low energy electrons (LEEs) of energies less than 20 eV are generated in large quantities by ionizing radiation in biological matter. While LEEs are known to induce single (SSBs) and double strand breaks (DSBs) in DNA, their ability to inactivate cells by inducing nonreparable lethal damage has not yet been demonstrated. Here we observe the effect of LEEs on the functionality of DNA, by measuring the efficiency of transforming Escherichia coli with a [pGEM-3Zf (-)] plasmid irradiated with 10 eV electrons. Highly ordered DNA films were prepared on pyrolitic graphite by molecular self-assembly using 1,3-diaminopropane ions (Dap(2+)). The uniformity of these films permits the inactivation of approximately 50% of the plasmids compared to <10% using previous methods, which is sufficient for the subsequent determination of their functionality. Upon LEE irradiation, the fraction of functional plasmids decreased exponentially with increasing electron fluence, while LEE-induced isolated base damage, frank DSB, and non DSB-cluster damage increased linearly with fluence. While DSBs can be toxic, their levels were too low to explain the loss of plasmid functionality observed upon LEE irradiation. Similarly, non-DSB cluster damage, revealed by transforming cluster damage into DSBs by digestion with repair enzymes, also occurred relatively infrequently. The exact nature of the lethal damage remains unknown, but it is probably a form of compact cluster damage in which the lesions are too close to be revealed by purified repair enzymes. In addition, this damage is either not repaired or is misrepaired by E. coli, since it results in plasmid inactivation, when they contain an average of three lesions. Comparison with previous results from a similar experiment performed with γ-irradiated plasmids indicates that the type of clustered DNA lesions, created directly on cellular DNA by LEEs, may be more difficult to repair than those produced by other species from radiolysis.
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Affiliation(s)
- Saloua Kouass Sahbani
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke , Sherbrooke, Quebec, Canada J1H 5N4
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21
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Ren X, Pflüger T, Weyland M, Baek WY, Rabus H, Ullrich J, Dorn A. An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of tetrahydrofuran with high mass and energy resolutions. J Chem Phys 2014; 141:134314. [DOI: 10.1063/1.4896614] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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22
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Stopping power for electrons in pyrimidine in the energy range 20–3000eV. Appl Radiat Isot 2014; 83 Pt B:91-4. [DOI: 10.1016/j.apradiso.2013.01.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 01/14/2013] [Accepted: 01/14/2013] [Indexed: 10/27/2022]
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23
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Storoniak P, Rak J, Ko YJ, Wang H, Bowen KH. Photoelectron spectroscopic and density functional theoretical studies of the 2′-deoxycytidine homodimer radical anion. J Chem Phys 2013; 139:075101. [DOI: 10.1063/1.4817779] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Boulanouar O, Fromm M, Bass AD, Cloutier P, Sanche L. Absolute cross section for loss of supercoiled topology induced by 10 eV electrons in highly uniform /DNA/1,3-diaminopropane films deposited on highly ordered pyrolitic graphite. J Chem Phys 2013; 139:055104. [PMID: 23927289 PMCID: PMC3812120 DOI: 10.1063/1.4817323] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It was recently shown that the affinity of doubly charged, 1-3 diaminopropane (Dap(2+)) for DNA permits the growth on highly ordered pyrolitic graphite (HOPG) substrates, of plasmid DNA films, of known uniform thickness [O. Boulanouar, A. Khatyr, G. Herlem, F. Palmino, L. Sanche, and M. Fromm, J. Phys. Chem. C 115, 21291-21298 (2011)]. Post-irradiation analysis by electrophoresis of such targets confirms that electron impact at 10 eV produces a maximum in the yield of single strand breaks that can be associated with the formation of a DNA(-) transient anion. Using a well-adapted deterministic survival model for the variation of electron damage with fluence and film thickness, we have determined an absolute cross section for strand-break damage by 10 eV electrons and inelastic scattering attenuation length in DNA-Dap complex films.
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Affiliation(s)
- Omar Boulanouar
- Laboratoire de Chimie Physique et Rayonnements – Alain Chambaudet, LRC CEA, UMR CNRS 6249, Université de Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France
| | - Michel Fromm
- Laboratoire de Chimie Physique et Rayonnements – Alain Chambaudet, LRC CEA, UMR CNRS 6249, Université de Franche-Comté, 16 route de Gray, F-25030 Besançon cedex, France
| | - Andrew D. Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Québec J1H 5N4, Canada
| | - Pierre Cloutier
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Québec J1H 5N4, Canada
| | - Léon Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Québec J1H 5N4, Canada
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25
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Śmiałek MA, Jones NC, Hoffmann SV, Mason NJ. Measuring the density of DNA films using ultraviolet-visible interferometry. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:060701. [PMID: 23848615 DOI: 10.1103/physreve.87.060701] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Indexed: 06/02/2023]
Abstract
In order to determine a proper value for the density of dry DNA films we have used a method based upon the measurement of interference effects in transmission spectra of thin DNA layers. Our results show that the methodology is effective and the density of DNA in this state, 1.407 g/cm(3), is much lower than the commonly used 1.7 g/cm(3). Obtaining accurate values for the DNA film density will allow the optical constants for DNA to be recalculated, which were previously obtained assuming a higher DNA density. Furthermore, since our recent investigations have shown a strong dependence of the sample composition on DNA film formation and thus on its density, such a method will be important in characterizing particle interactions with DNA film and their dose dependence.
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Affiliation(s)
- Małgorzata A Śmiałek
- Atomic Physics Division, Department of Atomic Physics and Luminescence, Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, 80-233 Gdańsk, Poland.
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26
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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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27
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Purkayastha S, Bernhard WA. What is the initial chemical precursor of DNA strand breaks generated by direct-type effects? J Phys Chem B 2012; 108:18377-82. [PMID: 17361311 PMCID: PMC1820892 DOI: 10.1021/jp048539x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The present study tests the hypothesis that the majority of DNA strand breaks produced by direct-type effects are due to sugar free radical precursors and that these radicals are produced by direct ionization of the sugar-phosphate backbone or by hole transfer to the sugar from tightly bound water. Well-defined crystalline DNA samples of d(CGCG)(2), d(CGCACG:GCGTGC), d(GTGCGCAC)(2), and d((GCACGCGTGC)(2) were irradiated at 4 K, and their free radical dose response determined from 0 to 1800 kGy. A model is proposed that effectively describes the dose response curves. It includes the following parameters: the free radical concentration at saturation C(max), the free radical yields G(b) and G(s), and the destruction constants k(b) and k(s). The subscripts b and s refer to base-centered and sugar-centered radicals, respectively. In each of these systems, the free radical concentration exhibits a remarkable resistance to dose saturation up to at least 1500 kGy. As predicted, G(b) > G(s), the G(b)/G(s) ratio varying between 4 and 12. Likewise, k(b) > k(s), the k(b)/k(s) ratio varying between 28 and 81. The lower cross-section for destruction of the sugar-centered radicals is consistent with the expectation that they are relatively radiation resistant. G(b)/G is between 0.81 and 0.92, indicating that at low doses the bases trap out 80-90% of the total free radical population. The remaining 10-20% are located on the sugar. At high dose, a larger fraction of the radicals are trapped on the backbone as seen from the ratio C(mxS)/C(mxB), which ranges from 3.5 to 8. This unusually late onset of dose saturation closely parallels that observed for strand break products in earlier studies. There is, therefore, a good correlation between the dose response profiles of sugar-trapped radicals and strand breaks. These observations strongly support the hypothesis that sugar radicals are precursors to the majority of strand breaks produced by the direct-type effect in DNA.
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Affiliation(s)
| | - William A. Bernhard
- * To whom correspondence should be addressed. E-mail: . Fax: (585) 275-6007. Phone: (585) 275-3730
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28
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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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29
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Park Y, Polska K, Rak J, Wagner JR, Sanche L. Fundamental mechanisms of DNA radiosensitization: damage induced by low-energy electrons in brominated oligonucleotide trimers. J Phys Chem B 2012; 116:9676-82. [PMID: 22812492 DOI: 10.1021/jp304964r] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The replacement of nucleobases with brominated analogs enhances DNA radiosensitivity. We examine the chemistry of low-energy electrons (LEEs) in this sensitization process by experiments with thin films of the oligonucleotide trimers TBrXT, where BrX = 5-BrU (5-bromouracil), 5-BrC (5-bromocytosine), 8-BrA (8-bromoadenine), or 8-BrG (8-bromoguanine). The products induced from irradiation of thin (∼ 2.5 nm) oligonucleotide films, with 10 eV electrons, under ultrahigh vacuum (UHV) are analyzed by HPLC-UV. The number of damaged brominated trimers ranges from about 12 to 15 × 10(-3) molecules per incident electron, whereas under the identical conditions, these numbers drop to 4-7 × 10(-3) for the same, but nonbrominated oligonucleotides. The results of HPLC analysis show that the main degradation pathway of trinucleotides containing brominated bases involve debromination (i.e., loss of the bromine atom and its replacement with a hydrogen atom). The electron-induced sum of products upon bromination increases by factors of 2.1 for the pyrimidines and 3.2 for the purines. Thus, substitution of any native nucleobase with a brominated one in simple models of DNA increases LEE-induced damage to DNA and hence its radiosensitivity. Furthermore, besides the brominated pyrimidines that have already been tested in clinical trials, brominated purines not only appear to be promising sensitizers for radiotherapy, but could provide a higher degree of radiosensitization.
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Affiliation(s)
- Yeunsoo Park
- Center for Radiobiology and Radiotherapy, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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30
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Fuss MC, Colmenares R, Sanz AG, Muñoz A, Oller JC, Blanco F, Do TPT, Brunger MJ, Almeida D, Limão-Vieira P, García G. Electron interactions with tetrahydrofuran. ACTA ACUST UNITED AC 2012. [DOI: 10.1088/1742-6596/373/1/012010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Chomicz L, Rak J, Storoniak P. Electron-induced elimination of the bromide anion from brominated nucleobases. A computational study. J Phys Chem B 2012; 116:5612-9. [PMID: 22510158 DOI: 10.1021/jp3008738] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The enhancement of radiodamage to DNA labeled with halonucleobases is attributed to the reactive radical produced from a halonucleobase by the attachment of an electron. We examined at the B3LYP/6-31++G** level electron capture by four brominated nucleobases (BrNBs): 8-bromo-9-methyladenine, 8-bromo-9-methylguanine, 5-bromo-1-methylcytosine, and 5-bromo-1-methyluracil followed by the release of the bromide anion and a nucleobase radical. We demonstrate that neutral BrNBs in both gas and aqueous phases are better electron acceptors than unsubstituted NBs and that resulting anion radicals, BrNBs(•-), can easily transform into the product complex of the bromide anion and the nucleobase radical ([Br(-)···NB(•)]). The overall thermodynamic stimulus for the process starting with the neutral BrNB and ending with the isolated bromide anion and the NB(•) radical is similar in the case of all four BrNBs studied, which suggests their comparable radiosensitizing capabilities.
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Affiliation(s)
- Lidia Chomicz
- Department of Chemistry, University of Gdańsk , Sobieskiego 18, 80-952 Gdańsk, Poland
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33
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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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35
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Do TPT, Leung M, Fuss M, Garcia G, Blanco F, Ratnavelu K, Brunger MJ. Excitation of electronic states in tetrahydrofuran by electron impact. J Chem Phys 2011; 134:144302. [DOI: 10.1063/1.3575454] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
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36
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D'Souza JS, Dharmadhikari JA, Dharmadhikari AK, Rao BJ, Mathur D. Effect of intense, ultrashort laser pulses on DNA plasmids in their native state: strand breakages induced by in situ electrons and radicals. PHYSICAL REVIEW LETTERS 2011; 106:118101. [PMID: 21469899 DOI: 10.1103/physrevlett.106.118101] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 02/07/2011] [Indexed: 05/24/2023]
Abstract
Single strand breaks are induced in DNA plasmids, pBR322 and pUC19, in aqueous media exposed to strong fields generated using ultrashort laser pulses (820 nm wavelength, 45 fs pulse duration, 1 kHz repetition rate) at intensities of 1-12 TW cm(-2). The strong fields generate, in situ, electrons and radicals that induce transformation of supercoiled DNA into relaxed DNA, the extent of which is quantified. Introduction of electron and radical scavengers inhibits DNA damage; results indicate that OH radicals are the primary (but not sole) cause of DNA damage.
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Affiliation(s)
- J S D'Souza
- UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina Campus, Mumbai 400 098, India
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Liljequist D. Discussion of coherent and incoherent contributions to the spatial distribution of very low energy electrons elastically scattered in liquid water. Radiat Phys Chem Oxf Engl 1993 2011. [DOI: 10.1016/j.radphyschem.2010.08.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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38
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Mirsaleh-Kohan N, Bass AD, Sanche L. Effect of morphology of thin DNA films on the electron stimulated desorption of anions. J Chem Phys 2011; 134:015102. [PMID: 21219028 PMCID: PMC3217040 DOI: 10.1063/1.3520562] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We present a comparison between the electron stimulated desorption (ESD) of anions from DNA samples prepared by lyophilization (an example of poorly organized or nonuniform films) and molecular self-assembly (well-ordered films). The lyophilization (or freeze- drying) method is perhaps the most frequently employed technique for forming DNA films for studies of low-energy electron (LEE) interactions leading to DNA damage; however, this technique usually produces nonuniform films with considerable clustering which may affect DNA configuration and enhance sample charging when the film is irradiated. Our results confirm the general validity of ESD measurements obtained with lyophilized samples, but also reveal limitations of lyophilization for LEE studies on DNA films. Specifically we observe some modulation of structures, associated with dissociative electron attachment, in the anion yield functions from different types of DNA film, confirming that conformational factors play a role in the LEE induced damage to DNA.
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Affiliation(s)
- Nasrin Mirsaleh-Kohan
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et les Sciences de Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
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39
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Massey S, Gallino E, Cloutier P, Tatoulian M, Sanche L, Mantovani D, Roy D. Low-energy electrons and X-ray irradiation effects on plasma-polymerized allylamine bioactive coatings for stents. Polym Degrad Stab 2010. [DOI: 10.1016/j.polymdegradstab.2009.11.037] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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40
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Fuss M, Muñoz A, Oller JC, Blanco F, Limão-Vieira P, Huerga C, Téllez M, Hubin-Fraskin MJ, Nixon K, Brunger M, García G. Modelling low energy electron interactions for biomedical uses of radiation. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/194/1/012028] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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41
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Śmiałek MA, Moore SA, Mason NJ, Shuker DEG. Quantification of Radiation-Induced Single-Strand Breaks in Plasmid DNA using a TUNEL/ELISA-Based Assay. Radiat Res 2009; 172:529-36. [DOI: 10.1667/rr1684.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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42
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Brun E, Cloutier P, Sicard-Roselli C, Fromm M, Sanche L. Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions. J Phys Chem B 2009; 113:10008-13. [PMID: 19603845 DOI: 10.1021/jp902540k] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively.
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Affiliation(s)
- Emilie Brun
- Laboratoire de Chimie Physique, CNRS UMR 8000, Université Paris-Sud 11, Bat. 350, 91405 Orsay Cedex, France
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43
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Wyer JA, Butterworth KT, Hirst DG, Latimer CJ, Montenegro EC, Shah MB, Currell FJ. Fragmentation and plasmid strand breaks in pure and gold-doped DNA irradiated by beams of fast hydrogen atoms. Phys Med Biol 2009; 54:4705-21. [PMID: 19590119 DOI: 10.1088/0031-9155/54/15/005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The results of an investigation into the damage caused to dry plasmid DNA after irradiation by fast (keV) hydrogen atoms are presented. Agarose gel electrophoresis was used to assess single and double strand break yields as a function of dose in dry DNA samples deposited on a mica substrate. Damage levels were observed to increase with beam energy. Strand break yields demonstrated a considerable dependence on sample structure and the method of sample preparation. Additionally, the effect of high-Z nanoparticles on damage levels was investigated by irradiating DNA samples containing controlled amounts of gold nanoparticles. In contrast to previous (photonic) studies, no enhancement of strand break yields was observed with the particles showing a slight radioprotective effect. A model of DNA damage as a function of dose has been constructed in terms of the probability for the creation of single and double strand breaks, per unit ion flux. This model provides quantitative conclusions about the effects of both gold nanoparticles and the different buffers used in performing the assays and, in addition, infers the proportion of multiply damaged fragments.
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Affiliation(s)
- J A Wyer
- Centre for Plasma Physics, IRCEP, Queen's University Belfast, BT7 1NN, UK.
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Zheng Y, Sanche L. Gold nanoparticles enhance DNA damage induced by anti-cancer drugs and radiation. Radiat Res 2009; 172:114-9. [PMID: 19580513 DOI: 10.1667/rr1689.1] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The chemotherapeutic agent cisplatin was chemically linked to pGEM-3Zf(-) plasmid DNA to produce a cisplatin-DNA complex, Gold nanoparticles, which bind electrostatically to pure DNA, could also be added to this complex. Dry films of pure plasmid DNA and DNA-cisplatin, DNA-gold nanoparticles and DNA-cisplatin-gold nanoparticles complexes were bombarded by 60 keV electrons. The yields of single- and double-strand breaks were measured as a function of exposure by electrophoresis. From a comparison of such yields from the different type of films, we found that the binding of only one gold nanoparticle to a plasmid-cisplatin complex containing 3197 base pairs increases by a factor of 3 the efficiency of the chemotherapeutic agent cisplatin to produce double-strand breaks in irradiated DNA. Furthermore, adding two cisplatin molecules and one gold nanoparticle to DNA enhances radiation-induced DSBs by a factor of 7.5. A number of phenomena could contribute to this huge enhancement, including the higher density of low-energy electrons and reactive species around the gold nanoparticles and the weakening of bonds adjacent to cisplatin in the DNA backbone. The addition of gold nanoparticles to cisplatin and other platinum agents may therefore provide interesting avenues of research to improve the treatment of cancer by concomitant chemoradiation.
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Affiliation(s)
- Yi Zheng
- Groupe en sciences des radiations, Faculté de médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Fujii K, Akamatsu K, Yokoya A. Decomposition of 2‐deoxy‐D‐ribose by irradiation with 0.6 keV electrons and by 0.5 keV ultrasoft X‐rays. Int J Radiat Biol 2009; 80:909-14. [PMID: 15764401 DOI: 10.1080/09553000400017721] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE To compare the molecular decomposition of 2-deoxy-D-ribose induced by 0.6 keV electron irradiation or by 0.5keV ultrasoft X-ray irradiation. MATERIALS AND METHODS A thin film of 2-deoxy-D-ribose was irradiated by two radiation sources: low-energy (approximately 0.6 keV) electrons and ultrasoft X-rays (approximately 0.5 keV). The positive ions that were desorbed from the sample during the irradiation were measured using a quadrupole mass spectrometer. The spectral changes in the X-ray absorption near edge structure (XANES) were also examined after the irradiation. RESULTS AND DISCUSSION The ions that were desorbed from 2-deoxy-D-ribose due to electron irradiation were mainly H+, CHx+, C2Hx+, CO+, CHxO+, C3Hx+, C2HxO+ and C3sHO+ (x=1, 2, and 3) ions. These ions were the same as those observed in desorption due to ultrasoft X-ray irradiation. The XANES spectral changes induced by electron irradiation showed C-O bond cleavage in the molecule and C=O bond formation in the surface residues. These results show that intensive molecular decomposition of the furanose ring structure was induced by both types of irradiation. It is inferred that these irradiation products are primarily produced by secondary electrons (several tens of eV), which are thought to be generated by both types of irradiation when they are applied to the 2-deoxy-D-ribose sample.
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Affiliation(s)
- Kentaro Fujii
- Radiation Risk Analysis Laboratory, Japan Atomic Energy Research Institute, 2-4 Shirakatashirane, Tokai, Ibaraki 319-1195 Japan.
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Muñoz A, Oiler JC, Blanco F, Gorfinkiel JD, Limão-Vieira P, Maira-Vidal A, Borge MJG, Tengblad O, Huerga C, Téllez M, García G. Energy deposition model based on electron scattering cross section data from water molecules. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/133/1/012002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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47
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Butterworth KT, Wyer JA, Brennan-Fournet M, Latimer CJ, Shah MB, Currell FJ, Hirst DG. Variation of strand break yield for plasmid DNA irradiated with high-Z metal nanoparticles. Radiat Res 2008; 170:381-7. [PMID: 18763863 DOI: 10.1667/rr1320.1] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Accepted: 04/29/2008] [Indexed: 04/11/2024]
Abstract
Using agarose gel electrophoresis, we measured the effectiveness of high-Z metal particles of different sizes on SSB and DSB yields for plasmid DNA irradiated with 160 kVp X rays. For plasmid samples prepared in Tris-EDTA buffer, gold nanoparticles were shown to increase G'(SSB) typically by a factor of greater than 2 while G'(DSB) increased by a factor of less than 2. Similar dose-modifying effects were also observed using gold microspheres. Addition of 10(-1) M DMSO typically decreased damage yields by a factor of less than 0.5. Plasmid samples prepared in PBS showed significantly different damage yields compared to those prepared in Tris-EDTA (P < 0.001) with G'(SSB) and G'(DSB) increasing by factors of 100 and 48, respectively. Furthermore, addition of gold nanoparticles to samples prepared in PBS decreased G'(SSB) and G'(DSB) by factors of 0.2 and 0.3, respectively. The results show plasmid damage yields to be highly dependent on differences in particle size between the micro- and nanometer scale, atomic number (Z) of the particle, and scavenging capacity of preparation buffers. This study provides further evidence using a plasmid DNA model system for the potential of high-Z metal nanoparticles as local dose-modifying agents.
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Affiliation(s)
- K T Butterworth
- Experimental Therapeutics Research Group, School of Pharmacy Queen's University Belfast Northern Ireland, BT9 7BL.
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49
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Liljequist D. A study of errors in trajectory simulation with relevance for 0.2–50eV electrons in liquid water. Radiat Phys Chem Oxf Engl 1993 2008. [DOI: 10.1016/j.radphyschem.2008.03.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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50
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Hunniford CA, Timson DJ, Davies RJH, McCullough RW. Effects of low energy carbon ions on plasmid DNA. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/101/1/012012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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