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Álvarez L, Bass AD, Lozano AI, García-Abenza A, Limão-Vieira P, Sanche L, García G. Electron stimulated desorption from condensed benzene. Phys Chem Chem Phys 2024; 26:9197-9206. [PMID: 38376884 DOI: 10.1039/d3cp06289a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
The electron induced dissociation of condensed benzene (C6H6) in thin films deposited on a Pt substrate is investigated by electron stimulated desorption (ESD) of anions and cations. The desorbed yields are recorded as a function of incident electron energy in the range of 10 to 950 eV for a fixed film thickness of 2 monolayers (ML) and for a fixed energy of 950 eV, as well as a function of film thickness from 0.5 to 8 monolayers (ML) for anions, and from 0.5 to 12ML for cations. Both energy and thickness dependencies are discussed in terms of the three main mechanisms yielding positively and/or negatively charged fragments: dissociative electron attachment (DEA), dipolar dissociation (DD) and dissociative ionization (DI) processes. At the probed energies, DD is the major mechanism, while DEA is predominantly induced by secondary electrons from the Pt substrate. Desorption of the parent positive ion is strongly suppressed. Similar qualitative behaviours are observed for the energy dependence of both anion and cation ESD yields, while some discrepancies exist in the thickness dependence, including a very significant systematic magnitude difference found between such ions formation. An estimation of the effective DD cross-section including the desorption probability is obtained. Feasible mechanisms behind the observed energy and thickness dependences for anion and cation yields are proposed. These results highlight the need for further investigations to better understand the underlying processes of electron induced dissociation in condensed matter.
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Affiliation(s)
- L Álvarez
- Fundamental Physics Institute, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, Madrid 28006, Spain.
| | - A D Bass
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Québec, Canada
| | - A I Lozano
- Fundamental Physics Institute, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, Madrid 28006, Spain.
- Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica 2829-516, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, 9 Avenue du Colonel Roche, Toulouse 31028, France
| | - A García-Abenza
- Fundamental Physics Institute, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, Madrid 28006, Spain.
- Spanish Meteorological Agency (AEMET), Murcia, Spain
| | - P Limão-Vieira
- Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica 2829-516, Portugal
| | - L Sanche
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, University of Sherbrooke, Québec, Canada
| | - G García
- Fundamental Physics Institute, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, Madrid 28006, Spain.
- Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia
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Behmand B, Noronha AM, Wilds CJ, Marignier JL, Mostafavi M, Wagner JR, Hunting DJ, Sanche L. Hydrated electrons induce the formation of interstrand cross-links in DNA modified by cisplatin adducts. J Radiat Res 2020; 61:343-351. [PMID: 32211848 PMCID: PMC7299263 DOI: 10.1093/jrr/rraa014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 01/17/2020] [Indexed: 06/10/2023]
Abstract
Double-stranded oligonucleotides containing cisplatin adducts, with and without a mismatched region, were exposed to hydrated electrons generated by gamma-rays. Gel electrophoresis analysis demonstrates the formation of cisplatin-interstrand crosslinks from the cisplatin-intrastrand species. The rate constant per base for the reaction between hydrated electrons and the double-stranded oligonucleotides with and without cisplatin containing a mismatched region was determined by pulse radiolysis to be 7 × 109 and 2 × 109 M-1 s-1, respectively. These results provide a better understanding of the radiosensitizing effect of cisplatin adducts in hypoxic tumors and of the formation of interstrand crosslinks, which are difficult for cells to repair.
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Affiliation(s)
- B Behmand
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4, Canada
| | - A M Noronha
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, H4B1R6, Canada
| | - C J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, H4B1R6, Canada
| | - J-L Marignier
- Centre de cinétique rapide ELYSE, Laboratoire de chimie physique, Université de Paris-Saclay 11, Orsay, France
| | - M Mostafavi
- Centre de cinétique rapide ELYSE, Laboratoire de chimie physique, Université de Paris-Saclay 11, Orsay, France
| | - J R Wagner
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4, Canada
| | - D J Hunting
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4, Canada
| | - L Sanche
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4, Canada
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Lemelin V, Bass AD, Sanche L. Low energy (6-18 eV) electron scattering from condensed thymidine (dT) III: absolute electronic excitation cross sections. Phys Chem Chem Phys 2020; 22:8364-8372. [PMID: 32266899 DOI: 10.1039/d0cp00198h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Absolute cross sections (CSs) for electronic excitation by low-energy electron (LEE) scattering, from condensed thymidine (dT) in the 6-18 eV incident energy range, were measured by high-resolution electron energy loss spectroscopy (HREELS). Various electron energy loss (EEL) spectra were acquired using 1 ML of dT condensed on a multilayer film of Ar held at about 20 K under ultra-high vacuum (∼1 × 10-11 Torr). dT is one of the most complex DNA constituents to be studied by HREELS and these spectra provide the first LEE energy-loss data for electronic excitation of a nucleoside. CSs for transitions to the states 13A', 13A'', 23A', 21A', 33A', 23A'', 43A', 33A'', 53A' and 51A' of dT were extracted from the EEL spectra. These states correlate to those previously measured for the thymine moiety. Two broad resonances are observed in the energy dependence of the CSs at around 8 and 10 eV; these energies are close to those found in earlier gas- and solid-phase studies on the interaction of LEEs with dT, thymine and related molecules. A quantitative comparison between the electronic CSs of dT and those of thymine and tetrahydrofuran indicates that no variation is induced in the electronic CSs of thymine upon chemically binding to a deoxyribose group.
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Affiliation(s)
- V Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des radiations, Université de Sherbrooke, Québec J1H 5N4, Canada.
| | - A D Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des radiations, Université de Sherbrooke, Québec J1H 5N4, Canada.
| | - L Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des radiations, Université de Sherbrooke, Québec J1H 5N4, Canada.
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Lemelin V, Bass AD, Cloutier P, Sanche L. Low energy (1-19 eV) electron scattering from condensed thymidine (dT) II: comparison of vibrational excitation cross sections with those of tetrahydrofuran and the recalibrated values of thymine. Phys Chem Chem Phys 2019; 21:23818-23825. [PMID: 31503272 DOI: 10.1039/c9cp03448j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Recent measurements of absolute vibrational cross sections (CSs) for low-energy electron (LEE) scattering from condensed thymidine (dT) allows comparison with CSs of its constituents; thymine and tetrahydrofuran (THF). To facilitate this comparison, the vibrational CSs of condensed thymine were remeasured at six electron incident energies and a correction was applied to the earlier thymine CS values measured by Lévesque et al. [Nucl. Instrum. Methods Phys. Res., Sect. B, 2003, 208, 225]. The incident energy dependence of the CS of each vibrational mode of dT is compared with the corresponding modes in thymine and/or THF. It is found that the magnitude of the CSs of the thymine breathing mode and the C-C stretch mode of THF are greatly attenuated in dT. Finally, the magnitudes of the total vibrational CSs of each molecule are compared. Below 4 eV, the total vibrational CSs of dT is greater than each of its two constituents. Interestingly, at higher energy (>6 eV), the magnitude of the total vibrational CS of dT is roughly equal to that of THF and is greater than thymine by only 15% at 10 eV, showing that the CSs of dT cannot be approximated by the addition of the CSs of its constituents over the entire energy range. These comparisons are discussed in terms of the basic principles involved in the formation and decay of shape resonances, which are known to be responsible for major enhancements of LEE-induced vibrational excitation at low electron energies.
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Affiliation(s)
- V Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des radiations, Université de Sherbrooke, Québec J1H 5N4, Canada.
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Lemelin V, Bass AD, Cloutier P, Sanche L. Low energy (1-19 eV) electron scattering from condensed thymidine (dT) I: absolute vibrational excitation cross sections. Phys Chem Chem Phys 2019; 21:23808-23817. [PMID: 31503266 DOI: 10.1039/c9cp03447a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Absolute cross sections (CSs) for vibrational excitation by electrons of energy between 1-19 eV scattering from condensed thymidine (dT) were measured by means of high-resolution electron energy loss spectroscopy (HREELS). The CSs were extracted from electron energy loss spectra of dT condensed on multilayers film of Ar held at about 20 K under ultra-high vacuum (∼1 × 10-11 Torr). dT is one of the most complex molecules to be studied in condensed phase by HREELS. The magnitudes of the vibrational CSs lie within the 10-17 cm2 range. Structures observed in the energy dependence of the vibrational CSs under 3 eV and around 4 eV were compared with previous results of gas- and solid-phase studies on dT and related molecules (e.g., thymine and tetrahydrofuran). These structures were attributed to the formation of shape resonances.
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Affiliation(s)
- V Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des radiations, Université de Sherbrooke, Québec J1H 5N4, Canada.
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Lemelin V, Bass AD, Sanche L. Note: Absolute electronic excitation cross sections for 8.5-17.5 eV electron scattering from condensed dimethyl phosphate (DMP). J Chem Phys 2018; 149:246101. [DOI: 10.1063/1.5059387] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- V. Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Québec J1H 5N4, Canada
| | - A. D. Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Québec J1H 5N4, Canada
| | - L. Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Québec J1H 5N4, Canada
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Ellis-Gibbings L, Bass AD, Cloutier P, García G, Sanche L. Electron stimulated desorption from condensed pyrimidine and pyridazine. Phys Chem Chem Phys 2018; 19:13038-13048. [PMID: 28484763 DOI: 10.1039/c7cp00715a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Low energy electron (LEE) interactions and the formation of transient negative ions play a dominant role in radiation-induced dissociation of condensed-phase biomolecules (e.g. in radiotherapy). Here we present data on the LEE-induced dissociation and desorption of the DNA/RNA-base and radiosensitizing agent analogues pyrimidine and pyridazine. Vapors of each molecule were condensed on either a Pt or Ar substrate to form a multilayer film or a submonolayer molecular target, respectively. These were irradiated with electrons of 0-80 eV and the desorbing anionic and cationic fragments analysed via time of flight mass spectrometry. The detected cations are the same species seen in gas-phase mass spectra, albeit of differing relative intensity. Anion yield functions exhibit strong maxima, indicating that transient negative ions contribute significantly, via dissociative electron attachment (DEA), to molecular dissociation below 20 eV. For both molecules, the <5 eV shape resonances, seen experimentally and predicted by theory, do not result in fragment desorption. The main anionic fragments are H- and CN- for both molecules, additionally the fragments C-, CH- C2H- and CHN- desorb from pyrimidine and C- and C2H- from pyridazine, with some resonances lying above the ionization limit. Pyrimidine shows higher anion desorption yields than pyridazine for all species except H-. The anion signal also comprises dipolar dissociation (DD), investigated in both anionic and cationic yield functions. From analysis of anion and cation yields, fragmentation pathways are suggested. The direct ionization pathway provides information on the appearance energies for cations and their production processes in condensed phase.
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Affiliation(s)
- L Ellis-Gibbings
- Fundamental Physics Institute, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain.
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Lemelin V, Bass AD, Wagner JR, Sanche L. Absolute vibrational excitation cross sections for 1-18 eV electron scattering from condensed dimethyl phosphate (DMP). J Chem Phys 2017; 147:234305. [DOI: 10.1063/1.5008486] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- V. Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - A. D. Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - J. R. Wagner
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - L. Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Michaud M, Fraser MJ, Sanche L. Low-energy electron-energy-loss spectroscopy of solid methanol : vibrational and electronic excitations. ACTA ACUST UNITED AC 2017. [DOI: 10.1051/jcp/1994911223] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Parenteau L, Sanche L. L'attachement dissociatif d'électrons de faible énergie (0-20 eV) sur le méthanol et diverses molécules organiques. ACTA ACUST UNITED AC 2017. [DOI: 10.1051/jcp/1994911237] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Lemelin V, Bass AD, Cloutier P, Sanche L. Absolute cross sections for electronic excitation of condensed tetrahydrofuran (THF) by 11-16 eV electrons. J Chem Phys 2017; 145:174703. [PMID: 27825202 DOI: 10.1063/1.4966650] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Absolute cross section (CS) data on the interaction of low energy electrons with DNA and its molecular constituents are required as input parameters in Monte-Carlo type simulations, for several radiobiological applications. Previously [V. Lemelin et al., J. Chem. Phys. 144, 074701 (2016)], we measured absolute vibrational CSs for low-energy electron scattering from condensed tetrahydrofuran, a convenient surrogate for the deoxyribose. Here we report absolute electronic CSs for energy losses of between 6 and 11.5 eV, by electrons with energies between 11 and 16 eV. The variation of these CSs with incident electron energy shows no evidence of transient anion states, consistent with theoretical and other experimental results, indicating that initial electron capture leading to DNA strand breaks occurs primarily on DNA bases or the phosphate group.
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Affiliation(s)
- V Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - A D Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - P Cloutier
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - L Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Lemelin V, Bass AD, Cloutier P, Sanche L. Absolute vibrational cross sections for 1-19 eV electron scattering from condensed tetrahydrofuran (THF). J Chem Phys 2016; 144:074701. [PMID: 26896993 PMCID: PMC5173351 DOI: 10.1063/1.4941377] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Absolute cross sections (CSs) for vibrational excitation by 1-19 eV electrons impacting on condensed tetrahydrofuran (THF) were measured with a high-resolution electron energy loss spectrometer. Experiments were performed under ultra-high vacuum (3 × 10(-11) Torr) at a temperature of about 20 K. The magnitudes of the vibrational CSs lie within the 10(-17) cm(2) range. Features observed near 4.5, 9.5, and 12.5 eV in the incident energy dependence of the CSs were compared to the results of theoretical calculations and other experiments on gas and solid-phase THF. These three resonances are attributed to the formation of shape or core-excited shape resonances. Another maximum observed around 2.5 eV is not found in the calculations but has been observed in gas-phase studies; it is attributed to the formation of a shape resonance.
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Affiliation(s)
- V Lemelin
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - A D Bass
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - P Cloutier
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - L Sanche
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences des Radiations, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Sahbani SK, Cloutier P, Bass AD, Hunting DJ, Sanche L. Electron Resonance Decay into a Biological Function: Decrease in Viability of E. coli Transformed by Plasmid DNA Irradiated with 0.5-18 eV Electrons. J Phys Chem Lett 2015; 6:3911-3914. [PMID: 26722892 PMCID: PMC5173358 DOI: 10.1021/acs.jpclett.5b01585] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Transient negative ions (TNIs) are ubiquitous in electron-molecule scattering at low electron impact energies (0-20 eV) and are particularly effective in damaging large biomolecules. Because ionizing radiation generates mostly 0-20 eV electrons, TNIs are expected to play important roles in cell mutagenesis and death during radiotherapeutic cancer treatment, although this hypothesis has never been directly verified. Here, we measure the efficiency of transforming E. coli bacteria by inserting into the cells, pGEM-3ZfL(-) plasmid DNA that confers resistance to the antibiotic ampicillin. Before transformation, plasmids are irradiated with electrons of specific energies between 0.5 and 18 eV. The loss of transformation efficiency plotted as a function of irradiation energy reveals TNIs at 5.5 and 9.5 eV, corresponding to similar states observed in the yields of DNA double strand breaks. We show that TNIs are detectable in the electron-energy dependence of a biological process and can decrease cell viability.
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Behmand B, Marignier JL, Mostafavi M, Wagner JR, Hunting DJ, Sanche L. Radiosensitization of DNA by Cisplatin Adducts Results from an Increase in the Rate Constant for the Reaction with Hydrated Electrons and Formation of Pt(I). J Phys Chem B 2015; 119:9496-500. [PMID: 26098937 DOI: 10.1021/acs.jpcb.5b01752] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pulse radiolysis measurements of the decay of hydrated electrons in solutions containing different concentrations of the oligonucleotide GTG with and without a cisplatin adduct show that the presence of a cisplatin moiety accelerates the reaction between hydrated electrons and the oligonucleotide. The rate constant of the reaction is found to be 2.23 × 10(10) mol(-1) L s(-1), which indicates that it is diffusion controlled. In addition, we show for the first time the formation of a Pt(I) intermediate as a result of the reaction of hydrated electrons with GTG-cisplatin. A putative reaction mechanism is proposed, which may form the basis of the radiosensitization of cancer cells in concomitant chemoradiation therapy with cisplatin.
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Affiliation(s)
- B Behmand
- †Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - J-L Marignier
- ‡Centre de cinétique rapide ELYSE, Laboratoire de chimie physique, Université de Paris-Sud 11, 91405, Orsay, France
| | - M Mostafavi
- ‡Centre de cinétique rapide ELYSE, Laboratoire de chimie physique, Université de Paris-Sud 11, 91405, Orsay, France
| | - J R Wagner
- †Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - D J Hunting
- †Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - L Sanche
- †Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Abstract
The oligonucleotide TTTTTGTGTTT with or without a cisplatin adduct was reacted with hydrated electrons generated by ionizing radiation. Hydroxyl radicals were quenched with ethylenediaminetetraacetic acid (EDTA), and the solutions were bubbled with wet nitrogen to eliminate oxygen, a scavenger of hydrated electrons. Prior to irradiation, the structure of the initial cisplatin adduct was identified by mass spectrometry as G-cisplatin-G. Radiation damage to DNA bases was quantified by high-performance liquid chromatography (HPLC), after enzymatic digestion of the TTTTTGTGTTT-cisplatin complex to deoxyribonucleosides. The masses of the platinum adducts following digestion and separation by HPLC were measured by mass spectrometry. Our results demonstrate that hydrated electrons induce damage to thymines as well as detachment of the cisplatin moiety from both guanines in the oligonucleotide. This detachment regenerates both unmodified guanine and damaged guanine, in equimolar amounts. At 1000 Gy, a net average of 2.5 thymines and 1 guanine are damaged for each platinum lost from the oligonucleotide. Given the extensive base damage that occurs for each cisplatin adduct lost, it is clear that, prior to undergoing detachment, these adducts must catalyze several cycles of reactions of hydrated electrons with DNA bases. It is likely that a single reaction leads to the loss of the cisplatin adduct and the damage observed on the guanine base; however, the damage to the thymine bases must require the continued presence of the cisplatin adduct, acting as a catalyst. To our knowledge, this is the first time that platinum-DNA adducts have been shown to have catalytic activity. We propose two pathways for the interaction of hydrated electrons with TTTTTGTGTTT-cisplatin: (1) the hydrated electron is initially captured by a thymine base and transferred by base to base electron hopping to the guanine site, where the cisplatin moiety detaches from the oligonucleotide via dissociative electron attachment, and (2) the hydrated electron interacts directly with the platinum-guanine adduct and induces detachment of the cisplatin moiety via dissociative electron attachment. Although the precise mechanism remains to be elucidated, our results provide important insights into the radiosensitization of DNA by cisplatin.
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Affiliation(s)
- B. Behmand
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - J. R. Wagner
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - L. Sanche
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - D. J. Hunting
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Kouass Sahbani S, Rezaee M, Cloutier P, Sanche L, Hunting DJ. Non-DSB clustered DNA lesions induced by ionizing radiation are largely responsible for the loss of plasmid DNA functionality in the presence of cisplatin. Chem Biol Interact 2014; 217:9-18. [PMID: 24732435 DOI: 10.1016/j.cbi.2014.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/18/2014] [Accepted: 04/03/2014] [Indexed: 10/25/2022]
Abstract
The combination of cisplatin and ionizing radiation (IR) increases cell toxicity by both enhancing DNA damage and inhibiting repair mechanisms. Although the formation of cluster DNA lesions, particularly double-strand breaks (DSB) at the site of cisplatin-DNA-adducts has been reported to induce cell death, the contribution of DSB and non-DSB cluster lesions to the cellular toxicity is still unknown. Although both lesions are toxic, it is not always possible to measure their frequency and cell survival in the same model system. To overcome this problem, here, we investigate the effect of cisplatin-adducts on the induction of DSB and non-DSB cluster DNA lesions by IR and determine the impact of such lesions on plasmid functionality. Cluster lesions are two or more lesions on opposite DNA strands with a short distance such that error free repair is difficult or impossible. At a ratio of two cisplatin per plasmid, irradiation of platinated DNA in solution with (137)Cs γ-rays shows enhancements in the formation of DNA DSB and non-DSB cluster lesions by factors of 2.6 and 2.1, respectively, compared to unmodified DNA. However, in absolute terms, the yield for non-DSB cluster lesions is far larger than that for DSB, by a factor of 26. Unmodified and cisplatin-modified DNA were irradiated and subsequently transformed into Escherichia coli to give survival curves representing the functionality of the plasmid DNA as a function of radiation dose. Our results demonstrate that non-DSB cluster lesions are the only toxic lesions present at a sufficient frequency to account for the loss of DNA functionality. Our data also show that Frank-DSB lesions are simply too infrequent to account for the loss of DNA functionality. In conclusion, non-DSB cluster DNA damage is known to be difficult to repair and is probably the lesion responsible for the loss of functionality of DNA modified by cisplatin.
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Affiliation(s)
- S Kouass Sahbani
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - M Rezaee
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - P Cloutier
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - L Sanche
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - D J Hunting
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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Behmand B, Cloutier P, Girouard S, Wagner JR, Sanche L, Hunting DJ. Hydrated electrons react with high specificity with cisplatin bound to single-stranded DNA. J Phys Chem B 2013; 117:15994-9. [PMID: 24205952 DOI: 10.1021/jp4089904] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Short oligonucleotides TTTTTGTGTTT and TTTTTTTGTTT in solution with and without cisplatin (cisPt) bound to the guanine bases were irradiated with γ-rays at doses varying from 0 to 2500 Gy. To determine the effect of hydrated electrons from water radiolysis on the oligonucleotides, we quenched (•)OH radicals with ethylenediaminetetraacetic acid (EDTA) and displaced oxygen, which reacts with hydrated electrons, by bubbling the solution with wet nitrogen. DNA strand breaks and platinum detachment were quantified by gel electrophoresis. Our results demonstrate that hydrated electrons react almost exclusively at the position of the cisPt adduct, where they induce cisPt detachment from one or both guanines in the oligonucleotide. Given the high yield of hydrated electrons in irradiated tissues, this reaction may be an important step in the mechanism of radiosensitization of DNA by cisPt.
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Affiliation(s)
- B Behmand
- Groupe en sciences des radiations, Faculté de médicine et des sciences de la santé, Université de Sherbrooke , Sherbrooke, Québec, Canada J1H 5N4
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20
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Michaud M, Bazin M, Sanche L. Nanodosimetry of Auger electrons: A case study from the decay of 125I and 0-18-eV electron stopping cross sections of cytosine. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 87:0327011-327014. [PMID: 24976798 PMCID: PMC4072652 DOI: 10.1103/physreve.87.0327011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Radiopharmaceuticals emitting Auger electrons are often injected into patients undergoing cancer treatment with targeted radionuclide therapy (TRT). In this type of radiotherapy, the radiation source is radial and most of the emitted primary particles are low-energy electrons (LEEs) having kinetic energies distributed mostly from zero to a few hundred electron volts with very short ranges in biological media. These LEEs generate a high density of energy deposits and clustered damage, thus offering a relative biological effectiveness comparable to that of alpha particles. In this paper, we present a simple model and corresponding measurements to assess the energy deposited near the site of the radiopharmaceuticals in TRT. As an example, a calculation is performed for the decay of a single 125I radionuclide surrounded by a 1-nm-radius spherical shell of cytosine molecules using the energy spectrum of LEEs emitted by 125I along with their stopping cross sections between 0 and 18 eV. The dose absorbed by the cytosine shell, which occupies a volume of 4 nm3, is extremely high. It amounts to 79 kGy per decay of which 3%, 39%, and 58% is attributed to vibrational excitations, electronic excitations, and ionization processes, respectively.
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Affiliation(s)
- M Michaud
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - M Bazin
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - L Sanche
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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21
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Abstract
The absolute cross sections (CSs) for vibrational excitations of cytosine by electron impact between 0.5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at monolayer coverage on an inert Ar substrate. The vibrational energies compare to those that have been reported from IR spectroscopy of cytosine isolated in Ar matrix, IR and Raman spectra of polycrystalline cytosine, and ab initio calculation. The CSs for the various H bending modes at 142 and 160 meV are both rising from their energy threshold up to 1.7 and 2.1 × 10(-17) cm(2) at about 4 eV, respectively, and then decrease moderately while maintaining some intensity at 18 eV. The latter trend is displayed as well for the CS assigned to the NH(2) scissor along with bending of all H at 179 meV. This overall behavior in electron-molecule collision is attributed to direct processes such as the dipole, quadrupole, and polarization contributions, etc. of the interaction of the incident electron with a molecule. The CSs for the ring deformation at 61 meV, the ring deformation with N-H symmetric wag at 77 meV, and the ring deformations with symmetric bending of all H at 119 meV exhibit common enhancement maxima at 1.5, 3.5, and 5.5 eV followed by a broad hump at about 12 eV, which are superimposed on the contribution due to the direct processes. At 3.5 eV, the CS values for the 61-, 77-, and 119-meV modes reach 4.0, 3.0, and 4.5 × 10(-17) cm(2), respectively. The CS for the C-C and C-O stretches at 202 meV, which dominates in the intermediate EEL region, rises sharply until 1.5 eV, reaches its maximum of 5.7 × 10(-17) cm(2) at 3.5 eV and then decreases toward 18 eV. The present vibrational enhancements, correspond to the features found around 1.5 and 4.5 eV in electron transmission spectroscopy (ETS) and those lying within 1.5-2.1 eV, 5.2-6.8 eV, and 9.5-10.9 eV range in dissociative electron attachment (DEA) experiments with cytosine in gas phase. While the ETS features are ascribed to shape resonances associated with the electron occupation of the second and third antibonding π-orbitals of the molecule in its ground state, the correspondence with DEA features suggests the existence of common precursor anion states decaying with certain probabilities into the vibrationally excited ground state.
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Affiliation(s)
- M Michaud
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
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Boudaïffa B, Cloutier P, Hunting D, Huels MA, Sanche L. Les électrons de très faible énergie produisent des lésions de l'ADN. Med Sci (Paris) 2012. [DOI: 10.4267/10608/1574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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23
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Pavel H, Ajeawung N, Faure R, Poirier D, Kamnasaran D, Ajeawung N, Joshi H, Kamnasaran D, Poirier D, Ajeawung N, Kamnasaran D, Lun X, Zemp F, Sun B, Stechishin O, Luchman A, Kelly JJ, Weiss S, Hamilton MG, Cairncross G, Senger DL, Bell J, McFadden G, Forsyth PA, Tzeng SY, Guerrero-Cazares H, Martinez EE, Young NP, Sunshine JC, Quinones-Hinojosa A, Green JJ, Lei L, D'Amico R, Sisti J, Leung R, Sonabend AM, Guarnieri P, Rosenfeld SS, Bruce JN, Canoll P, Baichwal VR, Reeves L, Chad BL, Zavitz KH, Beelen AP, Mather GG, Carlson RO, Manton C, Chandra J, Keir ST, Reardon DA, Saling JR, Gray LS, Bigner DD, Friedman HS, Zhang J, Brun J, Ogbomo H, Zemp F, Wang Z, Stojdl DJ, Lun X, Forsyth PA, Kong LY, Hatiboglu MA, Wei J, Wang Y, McEnery KA, Fuller GN, Qiao W, Davies MA, Priebe W, Heimberger AB, Amendolara B, Gil O, Lei L, Ivkovic S, Bruce J, Canoll P, Rosenfeld S, Finniss S, Perlstein B, Miller C, Okhrimenko H, Kazimirsky G, Cazacu S, Lemke N, Brodie S, Rempel SA, Rosenblum M, Mikkelsen T, Margel S, Brodie C, Guvenc H, Demir H, Gupta S, Mazumder S, Ray-Chaundhury A, Li T, Li C, Nakano I, Rahman R, Rahman C, Smith S, Macarthur D, Rose F, Shakesheff K, Grundy RG, Brenner AJ, Goins B, Bao A, Miller J, Trevino A, Zuniga R, Phillips WT, Gilg AG, Bowers KG, Toole BP, Maria BL, Leung GK, Sun S, Wong ST, Zhang XQ, Pu JK, Lui WM, Marino AM, Hussaini IM, Amos S, Simpson K, Redpath GT, Lyons C, Dipierro C, Grant GA, Wilson C, Salami S, Macaroni P, Li S, Park JY, Needham D, Bigner D, Dewhirst M, Ohlfest J, Gallardo J, Argawal S, Mittapalli R, Donelson R, Elmquist WF, Nicolaides T, Hariono S, Barkovich K, Hashizume R, Rowitch D, Weiss W, Sheer D, Baker S, Paugh B, Waldman T, Li H, Jones C, Forshew T, James D, Caroline H, Patrick R, Katrin L, Karl F, Ghazaleh T, Michael W, Albrecht V, Thorsteinsdottir J, Wagner E, Tonn JC, Ogris M, Schichor C, Charest G, Paquette B, Sanche L, Mathieu D, Fortin D, Qi X, Cuttitta F, Chu Z, Celerier J, Pakradouni J, Rixe O, Hashizume R, Gragg A, Muller S, Banerjee A, Phillips J, Prados M, Haas-Kogan D, Gupta N, James D, Florence L, Gwendoline VG, Veronique M, Robert K, Agarwal S, Mittapalli RK, Cen L, Carlson BL, Elmquist WF, Sarkaria JN, Sengupta S, Weeraratne SD, Rallapalli S, Amani V, Pierre-Francois J, Teider N, Rotenberg A, Cook J, Pomeroy SL, Jenses F, Cho YJ, Hjouj M, Last D, Guez D, Daniels D, Lavee J, Rubinsky B, Mardor Y, Serwer LP, Noble CO, Michaud K, Drummond DC, Ozawa T, Zhou Y, Marks JD, Bankiewicz K, Park JW, James D, Wang W, Cho H, Weintraub M, Jhaveri N, Torres S, Petasis N, Schonthal AH, Louie SG, Hofman FM, Chen TC, Grada Z, Hegde M, Schaffer DR, Ghazi A, Byrd T, Dotti G, Wels W, Heslop HE, Gottschalk S, Baker M, Ahmed N, Hamblett KJ, Kozlosky CJ, Liu H, Siu S, Arora T, Retter MW, Matsuda K, Hill JS, Fanslow WC, Diaz RJ, Etame A, Meaghan O, Mainprize T, Smith C, Hynynen K, Rutka J, Pradarelli J, Yoo JY, Kaka A, Alvarez-Breckenridge C, Pan Q, Chiocca EA, Teknos T, Kaur B, Lee SY, Slagle-Webb B, Sheehan JM, Connor JR, Cote J, Lepage M, Gobeil F, Fortin D, Kleijn A, Balvers R, Kloezeman J, Dirven C, Lamfers M, Leenstra S, See W, Tan IL, Nicolaides T, Pieper R, Jiang H, White E, Rios-Vicil CI, Yung WKA, Gomez-Manzano C, Fueyo J, Zemp FJ, McKenzie BA, Lun X, McFadden G, Forsyth PA, Mueller S, Yang X, Hashizume R, Gragg A, Smirnov I, Prados M, James DC, Phillips JJ, Berger MS, Rowitch DH, Gupta N, Haas-Kogan DH, D'Amico R, Lei L, Kennedy B, Rosenfeld SS, Canoll P, Bruce JN, Gopalakrishnan V, Das C, Taylor P, Kommagani R, Su X, Aguilera D, Thomas A, Wolff J, Flores E, Kadakia M, Alkins R, Broderson P, Sodhi R, Hynynen K, Chung SA, McDonald KL, Shen H, Day BW, Stringer BW, Johns T, Decollogne S, Teo C, Hogg PJ, Dilda PJ, Patel TR, Zhou J, Piepmeier JM, Saltzman WM, Vogelbaum MA, Agarwal S, Manchanda P, Ohlfest JR, Elmquist WF, Kitange GJ, Mladek AC, Carlson BL, Schroeder MA, Pokorny JL, Sarkaria JN, Ogbomo H, Lun X, Zhang J, McFadden G, Mody C, Forsyth P, Dasgupta T, Yang X, Hashizume R, Gragg A, Prados M, Nicolaides T, James CD, Haas-Kogan D, Madhankumar AB, Webb BS, Park A, Harbaugh K, Sheehan J, Connor JR. PRECLINICAL EXPERIMENTAL THERAPEUTICS AND PHARMACOLOGY. Neuro Oncol 2011. [DOI: 10.1093/neuonc/nor158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Jensen RL, Gilliespie D, Ajewung N, Faure R, Kamnasaran D, Ajewung N, Poirier D, Kamnasaran D, Tamura K, Wakimoto H, Rabkin SD, Martuza RL, Shah K, Hashizume R, Aoki Y, Serwer LP, Drummond D, Noble C, Park J, Bankiewicz K, James DC, Gupta N, Agerholm-Larsen B, Iversen HK, Jensen KS, Moller J, Ibsen P, Mahmood F, Gehl J, Corem E, Ram Z, Daniels D, Last D, Shneor R, Salomon S, Perlstein B, Margel S, Mardor Y, Charest G, Fortin D, Mathieu D, Sanche L, Paquette B, Li HF, Hashizume R, Aoki Y, Hariono S, Dasgupta T, Kim JS, Haas-Kogan D, Weiss WA, Gupta N, James CD, Waldman T, Nicolaides T, Ozawa T, Rao S, Sun H, Ng C, De La Torre J, Santos R, Prados M, James CD, Butowski N, Michaud K, Solomon DA, Li HF, Kim JS, Prados MD, Ozawa T, Waldman T, James CD, Pandya H, Gibo D, Debinski W, Vinchon-Petit S, Jarnet D, Jadaud E, Feuvret L, Garcion E, Menei P, Chen R, Yu JC, Liu C, Jaffer ZM, Chabala JC, Winssinger N, Rubenstein AE, Emdad L, Kothari H, Qadeer Z, Binello E, Germano I, Hirschberg H, Baek SK, Kwon YJ, Sun CH, Li SC, Madsen S, Debinski W, Liu T, Wang SW, Gibo DM, Fan QW, Cheng C, Hackett C, Feldman M, Houseman BT, Houseman BT, Nicolaides T, James CD, Haas-Kogan D, Oakes SA, Debnath J, Shokat KM, Weiss WA, Sai K, Chen F, Qiu Z, Mou Y, Zhang X, Yang Q, Chen Z, Patel TR, Zhou J, Piepmeier JM, Saltzman WM, Banerjee S, Kaul A, Gianino SM, Christians U, Gutmann DH, Wu J, Shen R, Puduvalli V, Koul D, Alfred Yung WK, Yun J, Sonabend A, Stuart M, Yanagihara T, Dashnaw S, Brown T, McCormick P, Romanov A, Sebastian M, Canoll P, Bruce JN, Piao L, Joshi K, Lee RJ, Nakano I, Madsen SJ, Chou CC, Blickenstaff JW, Sun CH, Zhou YH, Hirschberg H, Tome CML, Wykosky J, Palma E, Debinski W, Nduom E, Machaidze R, Kaluzova M, Wang Y, Nie S, Hadjipanayis C, Saito R, Nakamura T, Sonoda Y, Kumabe T, Tominaga T, Lun X, Zemp F, Zhou H, Stechishin O, Kelly JJ, Weiss S, Hamilton MG, Cairncross G, Rabinovich BA, Bell J, McFadden G, Senger DL, Forsyth PA, Kang P, Jane EP, Premkumar DR, Pollack IF, Yoo JY, Haseley A, Bratasz A, Powell K, Chiocca EA, Kaur B, Johns TG, Ferruzzi P, Mennillo F, De Rosa A, Rossi M, Giordano C, Magrini R, Benedetti G, Pericot GL, Magnoni L, Mori E, Thomas R, Tunici P, Bakker A, Yoo JY, Pradarelli J, Kaka A, Alvarez-Breckenridge C, Pan Q, Teknos T, Chiocca EA, Kaur B, Cen L, Ostrem JL, Schroeder MA, Mladek AC, Fink SR, Jenkins RB, Sarkaria JN, Madhankumar AB, Slagle-Webb B, Park A, Pang M, Klinger M, Harbaugh KS, Sheehan JM, Connor JR, Chen TC, Wang W, Hofman FM, Serwer LP, Michaud K, Drummond DC, Noble CO, Park JW, Ozawa T, James CD, Serwer LP, Noble CO, Michaud K, Drummond DC, Ozawa T, Zhou Y, Marks JD, Bankiewicz K, Park JW, James CD, Alonso MM, Gomez-Manzano C, Cortes-Santiago N, Roche FP, Fueyo J, Johannessen TCA, Grudic A, Tysnes BB, Nigro J, Bjerkvig R, Joshi AD, Parsons W, Velculescu VE, Riggins GJ, Bindra RS, Jasin M, Powell SN, Fu J, Koul D, Shen RJ, Colman H, Lang FF, Jensen MR, Alfred Yung WK, Friedman GK, Haas M, Cassady KA, Gillespie GY, Nguyen V, Murphy LT, Beauchamp AS, Hollingsworth CK, Debinski W, Mintz A, Pandya H, Garg S, Gibo D, Kridel S, Debinski W, Conrad CA, Madden T, Ji Y, Colman H, Priebe W, Seleverstov O, Purow BW, Grant GA, Wilson C, Campbell M, Humphries P, Li S, Li J, Johnson A, Bigner D, Dewhirst M, Sarkaria JN, Cen L, Pokorny JL, Mladek AC, Kitange GJ, Schroeder MA, Carlson BL, Suphangul M, Petro B, Mukhtar L, Baig MS, Villano J, Mahmud N, Keir ST, Reardon DA, Watson M, Shore GC, Bigner DD, Friedman HS, Keir ST, Gururangan S, Reardon DA, Bigner DD, Friedman HS. Pre-clinical Experimental Therapeutics and Pharmacology. Neuro Oncol 2010. [DOI: 10.1093/neuonc/noq116.s13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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25
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Abstract
The absolute cross sections (CSs) for electronic excitations of cytosine by electron impact between 5 and 18 eV were measured by electron-energy-loss (EEL) spectroscopy of the molecule deposited at low coverage on an inert Ar substrate. The lowest EEL features found at 3.55 and 4.02 eV are ascribed to transitions from the ground state to the two lowest triplet 1 (3)A(')(π→π(∗)) and 2 (3)A(')(π→π(∗)) valence states of the molecule. Their energy dependent CSs exhibit essentially a common maximum at about 6 eV with a value of 1.84×10(-17) cm(2) for the former and 4.94×10(-17) cm(2) for the latter. In contrast, the CS for the next EEL feature at 4.65 eV, which is ascribed to the optically allowed transition to the 2 (1)A(')(π→π(∗)) valence state, shows only a steep rise to about 1.04×10(-16) cm(2) followed by a monotonous decrease with the incident electron energy. The higher EEL features at 5.39, 6.18, 6.83, and 7.55 eV are assigned to the excitations of the 3 (3,1)A(')(π→π(∗)), 4 (1)A(')(π→π(∗)), 5 (1)A(')(π→π(∗)), and 6 (1)A(')(π→π(∗)) valence states, respectively. The CSs for the 3 (3,1)A(') and 4 (1)A(') states exhibit a common enhancement at about 10 eV superimposed on a more or less a steep rise, reaching, respectively, a maximum of 1.27 and 1.79×10(-16) cm(2), followed by a monotonous decrease. This latter enhancement and the maximum seen at about 6 eV in the lowest triplet states correspond to the core-excited electron resonances that have been found by dissociative electron attachment experiments with cytosine in the gas phase. The weak EEL feature found at 5.01 eV with a maximum CS of 3.8×10(-18) cm(2) near its excitation threshold is attributed to transitions from the ground state to the 1 (3,1)A(")(n→π(∗)) states. The monotonous rise of the EEL signal above 8 eV is attributed to the ionization of the molecule. It is partitioned into four excitation energy regions at about 8.55, 9.21, 9.83, and 11.53 eV, which correspond closely to the ionization energies of the four highest occupied molecular orbitals of cytosine. The sum of the ionization CS for these four excitation regions reaches a maximum of 8.1×10(-16) cm(2) at the incident energy of 13 eV.
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Affiliation(s)
- M. Bazin
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke Québec, Canada J1H 5N4
| | - M. Michaud
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke Québec, Canada J1H 5N4
| | - L. Sanche
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et Sciences de la Santé, Université de Sherbrooke, Sherbrooke Québec, Canada J1H 5N4
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Bazin M, Ptasinska S, Bass AD, Sanche L, Burean E, Swiderek P. Electron induced dissociation in the condensed-phase nitromethane: II. Desorption of neutral fragments. J Phys Condens Matter 2010; 22:084003. [PMID: 21389379 DOI: 10.1088/0953-8984/22/8/084003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Low energy electron induced dissociation in multilayer films of nitromethane (CD3NO2) was investigated by high resolution electron energy loss spectroscopy (HREELS) and by the electron stimulated desorption (ESD) of neutral species. HREELS measurements show that the lowest electronic states of the condensed molecule are very similar to those seen in the gas phase. Desorbed neutrals were detected using combined non-resonant multi-photon ionization at 355 nm and time of flight mass spectrometry. The most intense signals detected were those of CD3 (+) and NO (+) and are attributed primarily to the desorption of CD3 and NO2 fragments following molecular dissociation via low-lying electronic excited states of nitromethane (the detected NO (+) being the result of the dissociative ionization of NO2). By varying the time delay between the incident electron pulse and the ionizing laser pulse, it is possible to measure the kinetic energy distributions of desorbing fragments. The kinetic energy distributions above ∼ 5 eV appear invariant with incident electron energy, indicating that the same desorption process (dissociation via low-lying electronic states) operates at all the studied incident energies. Nevertheless, measurements of neutral yields as functions of incident electron energy demonstrate that excitation of the dissociative electronic states also proceeds via previously identified transient negative ions. At energies less than ∼ 5 eV, contributions from dissociative electron attachment are also observed in the yield of CD3 and other neutral fragments.
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Affiliation(s)
- M Bazin
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, J1H 5N4, Canada
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Abstract
It is well known that electrons below 15 eV induce strand breaks in DNA essentially via the formation of transient anions which decay by dissociative electron attachment (DEA) or into dissociative electronics states. The present article reports the results of a study on the influence of organic ions on this mechanism. tris and EDTA are incorporated at various concentrations within DNA films of different thicknesses. The amino group of tris molecules and the carboxylic acid function of ethylenediamine tetra-acetic acid (EDTA) molecules together can be taken as simple model for the amino acids components of proteins, such as histones, which are intimately associated with the DNA of eukaryotic cells. The yield of single strand breaks induced by 10 eV electrons is found to decrease dramatically as a function of the number of organic ions/nucleotide. As few as 2 organic ions/nucleotide are sufficient to decrease the yield of single strand breaks by 70%. This effect is partly explained by an increase in multiple inelastic electrons scattering with film thickness but changes in the resonance parameters can also contribute to DNA protection. This can occur if the electron captures cross section and the lifetime of the transient anions (i.e., core-excited resonances) formed at 10 eV are reduced by the presence of organic ions within the grooves of DNA. Moreover, it is proposed that the tris molecules may participate in the repair of DNA anions [such as G(-H)(-)] induced by DEA on DNA bases.
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Affiliation(s)
- A Dumont
- Research Center in Radiobiology and Radiotherapy (CR2), Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
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Yildirim Y, Balcan M, Bass AD, Cloutier P, Sanche L. Electron stimulated desorption of anions and cations from condensed allyl glycidyl ether. Phys Chem Chem Phys 2010; 12:7950-8. [DOI: 10.1039/b925347e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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29
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Jensen ET, Sanche L. Electron transfer reactions for image and image-derived states in dielectric thin films. J Chem Phys 2008; 129:074703. [DOI: 10.1063/1.2969105] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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30
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Menzel D, Cloutier P, Sanche L, Madey TE. Low-Energy Electron-Induced Processes in Fluorinated Copper Phthalocyanine Films Observed by F- Desorption: Why So Little Damage? J Phys Chem A 2007; 111:12427-33. [DOI: 10.1021/jp074269h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- D. Menzel
- Physik Department E20, Technische Universitaet Muenchen, D-85748 Garching, Germany, and Fritz-Haber-Institut der MPG, Department CP, Faradayweg 4-6, 14195 Berlin, Germany, Group in the Radiation Sciences, Faculté de Médecine, Université de Sherbrooke, 3001 12e avenue Nord, Sherbrooke, Quebec, Canada J1H 5N4, Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854
| | - P. Cloutier
- Physik Department E20, Technische Universitaet Muenchen, D-85748 Garching, Germany, and Fritz-Haber-Institut der MPG, Department CP, Faradayweg 4-6, 14195 Berlin, Germany, Group in the Radiation Sciences, Faculté de Médecine, Université de Sherbrooke, 3001 12e avenue Nord, Sherbrooke, Quebec, Canada J1H 5N4, Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854
| | - L. Sanche
- Physik Department E20, Technische Universitaet Muenchen, D-85748 Garching, Germany, and Fritz-Haber-Institut der MPG, Department CP, Faradayweg 4-6, 14195 Berlin, Germany, Group in the Radiation Sciences, Faculté de Médecine, Université de Sherbrooke, 3001 12e avenue Nord, Sherbrooke, Quebec, Canada J1H 5N4, Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854
| | - T. E. Madey
- Physik Department E20, Technische Universitaet Muenchen, D-85748 Garching, Germany, and Fritz-Haber-Institut der MPG, Department CP, Faradayweg 4-6, 14195 Berlin, Germany, Group in the Radiation Sciences, Faculté de Médecine, Université de Sherbrooke, 3001 12e avenue Nord, Sherbrooke, Quebec, Canada J1H 5N4, Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, 136 Frelinghuysen Road, Piscataway, New Jersey 08854
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31
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Hedhili MN, Cloutier P, Bass AD, Madey TE, Sanche L. Electron stimulated desorption of anionic fragments from films of pure and electron-irradiated thiophene. J Chem Phys 2007; 125:094704. [PMID: 16965102 DOI: 10.1063/1.2338030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electron stimulated desorption (ESD) of anions is used to explore the effects of electron irradiation on a thiophene film and we report measurements for electron impact on multilayer thiophene condensed on a polycrystalline platinum substrate. Below 22 eV and at low electron dose, desorbed anions include H- (the dominant signal) as well as S-, CH2-, SH- and SCH2-. Yield functions show that anions are desorbed both by dissociative electron attachment (DEA) with resonances observed at 9.5, 11, and 16 eV, and for energies >13 eV, by dipolar dissociation (DD). An increase in the S- signal from electron irradiated (beam-damaged) thiophene films and the appearance of a new DEA resonance in the S- yield function at 6 eV are linked to rupture of the thiophene ring and the formation of sulfur-terminated products within the film. The threshold energy for ring rupture is 5 eV. The desorption of new anions such as C4H3S- (Thiophene-H)- is also observed from electron irradiated films and these likely arise from the decomposition of large radiation product molecules synthesized in the film. The yield functions of H-, S-, SH-, (Thiophene-H)-, and (Thiophene+H)- anions from irradiated thiophene films that have been annealed to 300 K, each exhibit a single resonant feature centered around 5.1 eV, suggesting that all signals derive from DEA to the same molecular radiation product. In contrast, only H- and S- are observed to desorb from films of 2-2-bithiophene and no resonance is seen below approximately 10 eV in the anion yield functions. These data suggest that electron irradiation causes formation of ring-opened oligomers, and that closed-ring or 'classical" oligomers, (similar to bithiophene) if formed, contribute little to the ESD of anions.
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Affiliation(s)
- M N Hedhili
- Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 -8019, USA
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32
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Affiliation(s)
- R Naaman
- Department of Chemical Physics, Weizmann Institute, Rehovot, Israel 76100
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33
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Abstract
We report the mass spectrometric measurement of anions desorbed by 3-24 eV electron impact on thin films of formamide-1-d (DCONH2) and on the self-assembled monolayer (SAM) of two different Lys amide molecules used as a molecular model of the peptide backbone. In the present SAM configuration, the amides are elevated from a gold substrate by hydrocarbon chains to remove the effects of the metal substrate. Electron irradiation produces H- and D- from the formamide-1-d film and H-, CH3-, O-, and OH- from the SAM Lys amides. Below 13 eV, the dependence of the anion yields on the incident electron energy exhibits structures indicative of the dissociative electron attachment process, which is responsible for molecular fragmentation via the initial formation of core-excited anions. Above 13 eV, anion desorption is dominated principally by non-resonant dipolar dissociation. Our results suggest that the sensitivity of the peptide backbone to secondary electrons produced by ionizing radiation depends on the chemical environment (i.e., the amino acids sequence).
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Affiliation(s)
- P Cloutier
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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34
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Michaud M, Hébert EM, Cloutier P, Sanche L. Electron photoemission from charged films: Absolute cross section for trapping 0–5eV electrons in condensed CO2. J Chem Phys 2007; 126:024701. [PMID: 17228960 DOI: 10.1063/1.2404647] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electron trapping or attachment cross section of carbon dioxide (CO2) condensed as thin films on a spacer of Ar is obtained using a simple model for electron trapping in a molecular film and then charge releasing from the same film by photon absorption. The measurements are presented for different electron exposures and impact energies, film thicknesses, and probing photon energies. The cross section for trapping an electron of incident energy between 0 and 5 eV reveals three different attachment processes characterized by a maximum at about 0.75 eV, a structured feature around 2.25 eV, and a shoulder around 3.75 eV. From the measurement of their dependence with the probing photon energy, the two lowest processes produce traps having a vertical electron binding energy of approximately 3.5 eV, whereas the highest one yields a slightly higher value of approximately 3.7 eV. The 0.75 eV maximum corresponds to the formation of vibrational Feshbach resonances in (CO2)n- anion clusters. The 2.25 eV feature is attributed to the formation of a vibrationally excited 2Piu anion in (CO2)n- clusters, followed by fast decay into its vibrational ground state without undergoing autodetachment. Finally, 3.75 eV shoulder is assigned to the well-known dissociative electron attachment process from 2Piu anion state producing the O- anion in the gas phase and the (CO2)nO- anions in clusters.
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Affiliation(s)
- M Michaud
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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35
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Deschamps MC, Michaud M, Sanche L. Low-energy electron scattering cross section for the production of CO within solid films of carbon dioxide. J Chem Phys 2006; 121:4284-91. [PMID: 15332976 DOI: 10.1063/1.1779570] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We report absolute electron scattering cross sections sigma(p) for the production of CO within thin solid film of carbon dioxide (CO(2)) condensed on a solid Ar substrate. The CO fragments, which remain trapped within the bulk of the carbon dioxide film, are detected in situ by recording energy losses to their lowest triplet electronic state a (3)Pi using high-resolution electron-energy-loss spectroscopy. The production of CO is studied as a function of the electron exposure, film thickness, and incident electron energy between 2 and 30 eV, a range within which most of the secondary electrons are created in systems irradiated by high-energy particles. The energy dependence is characterized by a feature around 4 eV with sigma(p)=(7.0+/-4.0)x10(-18) cm(2), a minimum around 7 eV, a strong rise up to a large and broad maximum around 15 eV with sigma(p)=(5.4+/-2.5)x10(-17) cm(2), a decrease to a minimum around 18.5 eV, and finally a monotonous increase up to 30 eV. The CO production is discussed in terms of the formation of electron resonances or transient anion states, which may lead directly to the fragmentation of the molecule via dissociative electron attachment or indirectly by decaying into an entirely repulsive part of the corresponding excited neutral and positive ion states.
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Affiliation(s)
- M C Deschamps
- Departement de Medecine Nucleaire et Radiobiologie, Faculte de Medecine, Universite de Sherbrooke, Sherbrooke Quebec J1H 5N4, Canada
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36
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37
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Cecchini S, Girouard S, Huels MA, Sanche L, Hunting DJ. Response to Dr. Ward's Comments. Radiat Res 2005. [DOI: 10.1667/rr3411.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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38
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Levesque PL, Michaud M, Cho W, Sanche L. Absolute electronic excitation cross sections for low-energy electron (5–12eV) scattering from condensed thymine. J Chem Phys 2005; 122:224704. [PMID: 15974700 DOI: 10.1063/1.1925610] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The absolute cross sections for electronic excitations of thymine by electron impact between 5 and 12 eV are determined by means of electron-energy loss (EEL) spectroscopy for the molecule deposited at submonolayer coverage on an inert Ar substrate. The lowest EEL features at 3.7 and 4.0 eV are attributed to the excitation of the triplet 1 3A'(pi --> pi*) and 1 3A''(n --> pi*) valence states of the molecule. The higher EEL features located at 4.9, 6.3, 7.3, and 9 eV with a weak shoulder around 6 eV are ascribed mostly to triplet valence (pi --> pi*) excitation manifold of the molecule. The energy dependence of the cross section for both the lowest triplet valence excitations shows essentially a peak at about 5 eV reaching a value of 2.9 x 10(-17) cm2. The cross sections for the higher EEL features are generally characterized by a common broad maximum around 8 eV. The latter reaches a value of 1.36 x 10(-16) cm2 for the combined 6 and 6.3 eV excitation region. The maxima in the present cross sections are found to correspond to the resonances that have been reported at about the same energies in the O- yield from electron impact on thymine in the gas phase.
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Affiliation(s)
- P L Levesque
- Groupe en Sciences des Radiations, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
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39
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Abstract
We report results on the desorption of OH- induced by 0-19 eV electrons incident on self-assembled monolayer films made of single and double DNA strands of different orientations with respect to a gold substrate. Such measurements make it possible to deduce the mechanism and site of OH- formation within a biomolecule as complex as DNA. This type of damage is attributed to dissociative electron attachment to the phosphate group of DNA, when it contains the counterion H+.
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Affiliation(s)
- X Pan
- Group in the Radiation Sciences, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, University of Sherbrooke, Quebec, Canada
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40
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Levesque PL, Michaud M, Sanche L. Absolute vibrational and electronic cross sections for low-energy electron (2–12 eV) scattering from condensed pyrimidine. J Chem Phys 2005; 122:094701. [PMID: 15836156 DOI: 10.1063/1.1854121] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Low-energy vibrational and electronic electron-energy-loss (EEL) spectra of pyrimidine condensed on a thin film of solid argon held at 18 K are reported for the incident-energy range of 2-12 eV. Sensitivity to symmetry and spin forbidden transitions as well as correlations to the triplet states of benzene make it possible to ascribe the main features, below 7 eV in the electronic part of the EEL spectrum, to triplet transitions. The lowest EEL feature with an energy onset at 3.5 eV is attributed to a transition to the (3)B(1)(n-->pi(*)) valence electronic state and the next triplet n-->pi(*) transition to a (3)A(2) state located around 4.5 eV. The remaining EEL features at 4.3, 5.2, 5.8, and 6.5 eV are all assigned to pi-->pi(*) transitions to states of symmetry (3)B(2), (3)A(1), (3)B(2), and (3)B(2)+(3)A(1), respectively. The most intense maximum at 7.6 eV is found to correspond to both (1)B(2) and (1)A(1) transitions, as in the vacuum ultraviolet spectra. Absolute inelastic cross sections per scatterer are derived from a single collision treatment described herein. Their values are found to lie within the 10(-17) cm(2) range for both the electronic and the vibrational excitations. Features in the energy dependence of the cross sections are discussed, whenever possible, by comparison with data and mechanisms found in the gas phase. A maximum over the 4-5 eV range is attributed to a B (2)B(1) shape resonance and another one observed in the 6-7 eV range is ascribed to either or both sigma(*) shape resonances of (2)A(1) and (2)B(2) symmetries.
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Affiliation(s)
- P L Levesque
- Groupe en Science des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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41
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Abstract
The effects of bromodeoxyuridine (BrdUrd) substitution for thymidine on gamma-ray-induced strand breakage were determined in single- and double-stranded oligonucleotides and double-stranded oligonucleotides containing a mismatched bubble region. BrdUrd does not sensitize complementary double-stranded DNA to gamma-ray-induced strand breakage, but it greatly sensitizes single-stranded DNA. However, when the BrdUrd is present in a single-stranded bubble of a double-stranded oligonucleotide, the non-base-paired nucleotides adjacent to the BrdUrd as well as several unpaired sites on the opposite unsubstituted strand are strongly sensitized. The radiosensitization properties of BrdUrd result primarily from the electrophilic nature of the bromine, making it a good leaving group and leading to the irreversible formation of the uridine-yl radical (dUrd(.)) or the uridine-yl anion (dUrd(-)) upon addition of an electron. The radiolytic loss of the bromine atom is greatly suppressed in double-stranded compared to single-stranded DNA. Thus we propose that the radiosensitization effects of bromouracil in vivo will likely be limited to single-strand regions such as found in transcription bubbles, replication forks, DNA bulges and the loop region of telomeres. Our results may have profound implications for the clinical use of bromodeoxyuridine (BrdUrd) as a radiosensitizer as well as for the development of targeted radiosensitizers.
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Affiliation(s)
- S Cecchini
- Group in the Radiation Sciences, Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
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42
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Lu QB, Sanche L. Enhancements in dissociative electron attachment to CF4, chlorofluorocarbons and hydrochlorofluorocarbons adsorbed on H2O ice. J Chem Phys 2004; 120:2434-8. [PMID: 15268383 DOI: 10.1063/1.1637335] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report that the absolute cross sections for dissociative attachment of approximately 0 eV electrons to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are strongly enhanced by the presence of H2O ice. The absolute cross sections for CFCl3, CHF2Cl, and CH3CF2Cl on water ice are measured to be approximately 8.9 x 10(-14), approximately 5.1 x 10(-15), and approximately 4.9 x 10(-15) cm2 at approximately 0 eV, respectively. The former value is about 1 order of magnitude higher than that in the gas phase, while the latter two are 3-4 orders higher. In contrast, the resonances at electron energies > or = 2.0 eV are strongly suppressed either for CFCs and HCFCs or for CF4 adsorbed on H2O ice. The cross-section enhancement is interpreted to be due to electron transfer from precursor states of the solvated electron in ice to an unfilled molecular orbital of CFCs or HCFCs followed by its dissociation. This study indicates that electron-induced dissociation is a significant process leading to CFC and HCFC fragmentation on ice surfaces.
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Affiliation(s)
- Q-B Lu
- Group of the Canadian Institutes of Health Research in the Radiation Sciences, Faculty of Medicine, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
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43
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Abstract
We investigated vibrational and electronic excitations of 0.1-layer up to 2.4-layer film of H(2)O deposited on a 1.4-layer film of thymine condensed on Ar at a temperature of 18 K using high-resolution electron-energy loss (EEL) spectroscopy at the incident energy of 12 eV. The spectral contribution originating essentially from the H(2)O overlayer is obtained by separating the measured contribution from the underlying film of thymine, considering the electron beam attenuation in the H(2)O overlayer. The vibrational EEL spectrum of submonolayer amount of H(2)O on thymine, which excepts for small energy shift of the vibrational bands, is found to compare in intensity to that of the same amount of H(2)O deposited directly on the argon. The electronic energy-loss intensity near 8.6 eV, which is attributed to the excitation of (3,1)B(1) states of H(2)O in condensed phase, is observed to decrease by a factor of about 3 by the presence of the underlying film of thymine. This indicates that the corresponding cross section for excitation the (3,1)B(1) states of H(2)O by the electron impact is reduced significantly by the close proximity of the thymine molecules.
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Affiliation(s)
- W Cho
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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Breton SP, Michaud M, Jäggle C, Swiderek P, Sanche L. Damage induced by low-energy electrons in solid films of tetrahydrofuran. J Chem Phys 2004; 121:11240-9. [PMID: 15634080 DOI: 10.1063/1.1814632] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We report on the low-energy electron-induced production of aldehydes within thin solid films of tetrahydrofuran (THF) condensed on a solid Kr substrate. The aldehyde fragments, which remain trapped within the bulk of the THF film, are detected in situ via their 3,1(n-->pi*) and 3(pi-->pi*) electronic transitions and vibrational excitations in the ground state using high-resolution electron-energy-loss spectroscopy. The production of aldehyde is studied as a function of the electron exposure, film thickness, and incident electron energy between 1 and 18.5 eV. The aldehyde production is calibrated in terms of an electron scattering cross section, which is found to be typically 6-7 x 10(-17) cm(2) between 11 and 19 eV. Its energy dependence is characterized by a small feature around 3 eV, a strong rise from 6 eV up to a maximum at 12.5 eV, followed by two structures centered around 15 and 18 eV. The aldehyde production is discussed in terms of the formation of electron resonances or transient anion states, which may lead to the fragmentation of the molecule and explain the structures seen in the energy dependence of the measured cross section.
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Affiliation(s)
- S-P Breton
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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45
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Abdoul-Carime H, Sanche L. Alteration of Protein Constituents Induced by Low-Energy (<40 eV) Electrons. III. The Aliphatic Amino Acids. J Phys Chem B 2003. [DOI: 10.1021/jp030413x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H. Abdoul-Carime
- Groupe des Instituts de Recherche en Santé du Canada, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
| | - L. Sanche
- Groupe des Instituts de Recherche en Santé du Canada, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
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46
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Deschamps MC, Michaud M, Sanche L. Low-energy electron-energy-loss spectroscopy of electronic transitions in solid carbon dioxide. J Chem Phys 2003. [DOI: 10.1063/1.1615754] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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47
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Abstract
We propose a framework to calculate the intermolecular multiple elastic scattering of low-energy electrons from helical macromolecules and indicate how it affects the resonant capture cross section. Using a model of DNA, an appreciable enhancement of the elastic and resonant capture cross sections is predicted at incident energies below 15 eV. These results may qualitatively explain the observed prominence of low-energy resonances in strand breaking of plasmid DNA.
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Affiliation(s)
- L G Caron
- Groupe des Instituts de Recherche en Santé du Canada en Sciences des Radiations, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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48
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Lu QB, Sanche L. Condensed-phase effects on absolute cross sections for dissociative electron attachment to CFCs and HCFCs adsorbed on Kr. J Chem Phys 2003. [DOI: 10.1063/1.1587688] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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49
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Abdoul-Carime H, Sanche L. Alteration of protein constituents induced by low-energy (<35 eV) electrons: II. Dissociative electron attachment to amino acids containing cyclic groups. Radiat Res 2003; 160:86-94. [PMID: 12816527 DOI: 10.1667/rr3025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We report measurements of the desorption of anions from thin condensed films of tryptophan (Trp), histidine (His) and proline (Pro) stimulated by 5-35 eV electron impact. H-, O-, OH- and CN- desorb from Trp, His and Pro, whereas CH2- is observed only from Pro fragmentation. Below 12 eV, the anion yield functions exhibit resonant structures indicative of dissociative electron attachment. For all three amino acids, this process is likely to be initiated by the resonant capture of the incident electron at the NH3(+)-CH-.....-COO- and/or NH2-CH-.....-COOH group of the molecule. Temporary electron attachment to the ring leads to anion desorption only for tryptophan and proline. The energy-averaged yields measured at the detector of the mass spectrometer are (4.9, 0.3 and 54.0) x 10(-8) H-/incident electron and (3.4, 2.9, 1.8) x 10(-11) O-/incident electron, respectively, from Trp, His and Pro dissociation. Fragmentation of amino acids is found to be as intense as that of the nucleic acid bases. These results are discussed within the context of radiobiological damage induced by secondary electrons.
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Affiliation(s)
- H Abdoul-Carime
- Groupe des Instituts de Recherche en Santé du Canada en Sciences des Radiations, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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50
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Abstract
Electron-stimulated desorption of anions from thin films of linear and supercoiled DNA is investigated in the range 3-20 eV. Resonant structures are observed with maxima at 9.4+/-0.3, 9.2+/-0.3, and 9.2+/-0.3 eV, respectively, in the yield dependence of H-, O-, and OH- on the incident electron energy. Their formation is attributed to dissociative electron attachment.
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Affiliation(s)
- X Pan
- Group of the Canadian Institutes of Health Research in the Radiation Sciences, Faculté de médecine, Université de Sherbrooke, Sherbrooke (QC) Canada J1H 5N4
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