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Michaud M, Wen A, Sanche L. Cross sections for low-energy (1-100 eV) electron elastic and inelastic scattering in amorphous ice. Radiat Res 2003; 159:3-22. [PMID: 12492364 DOI: 10.1667/0033-7587(2003)159[0003:csflee]2.0.co;2] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We report the integral cross sections per scatterer (i.e. elastic collision, phonon excitations, vibrational excitations, electronic excitations and ionization) for 1-100 eV electron scattering in an amorphous film of ice condensed at a temperature of 14 K. The integral cross sections are determined relative to the total from a two-stream multiple-scattering analysis of the electron energy distribution backscattered from the film. Their energy dependence is obtained from both the analysis of the elastic electron reflectivity as a function of the film thickness and the vibrational electron energy-loss spectra measured for several incident energies and large film thickness. The magnitude and various features found in the energy dependence of the cross sections are discussed, whenever possible, by comparison with data and with scattering mechanisms available in the gas phase. Microcospic effects, which are implicitly included in cross sections determined in this way, are discussed in terms of interference and coherent multiple-scattering contributions among the scattering sites as well as interactions of the scattering sites with their neighbors in the condensed phase.
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Michaud M, Wen A, Sanche L. Cross Sections for Low-Energy (1–100 eV) Electron Elastic and Inelastic Scattering in Amorphous Ice. Radiat Res 2003. [DOI: 10.1667/0033-7587(2003)159%5b0003:csflee%5d2.0.co;2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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53
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Abdoul-Carime H, Sanche L. Mechanism for Anion and Sulfur-Radical Production by 1−18 eV Electron Impact on Dimethyl Disulfide Adsorbed on Ice. J Phys Chem B 2002. [DOI: 10.1021/jp0206525] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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54
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Abdoul-Carime H, Cecchini S, Sanche L. Alteration of protein structure induced by low-energy (<18 eV) electrons. I. The peptide and disulfide bridges. Radiat Res 2002; 158:23-31. [PMID: 12071800 DOI: 10.1667/0033-7587(2002)158[0023:aopsib]2.0.co;2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We present measurements of low-energy (<18 eV) electron-stimulated desorption of anions from acetamide (CH(3)CONH(2)) and dimethyl disulfide [DMDS: (CH(3)S)(2)] films. Electron irradiation of physisorbed CH(3)CONH(2) produces H(-), CH(3)(-) and O(-) anions, whereas the H(-), CH(2)(-), CH(3)(-), S(-), SH(-) and SCH(3)(-) anions are observed to desorb from the DMDS film. Below 12 eV, the dependence of the anion yields on the incident electron energy exhibits structures that indicate that a resonant process (i.e. dissociative electron attachment) is responsible for molecular fragmentation. Within the range of 1-18 eV, it is found that (1.7 and 1.4) x 10(7) H(-) ions/incident electron and (7.8 x 10(-11) and 4.3 x 10(-8)) of the other ions/incident electron are desorbed from acetamide and DMDS films, respectively. These results suggest that, within proteins, the disulfide bond is more sensitive to low-energy electron attack than the peptide bond. In biological cells, some proteins interact closely with nucleic acid. Therefore, the observed fragments, when produced from secondary low-energy electrons generated by high-energy radiation, not only may denature proteins, but may also induce reactions with the nearby nucleic acid and damage DNA.
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Leclerc G, Cui Z, Sanche L. Effective dissociation cross section for the low-energy (0.5-31 eV) electron impact on solid hexane thin films. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100310a008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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56
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Leclerc G, Goulet T, Cloutier P, Jay-Gerin JP, Sanche L. Low-energy (0-10 eV) electron transmission spectra of multilayer tryptophan films. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100303a020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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57
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Rowntree P, Parenteau L, Sanche L. Anion yields produced by low-energy electron impact on condensed hydrocarbon films. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100165a054] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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58
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Parenteau L, Jay-Gerin JP, Sanche L. Electron-Stimulated Desorption of H- Ions via Dissociative Electron Attachment in Condensed Methanol. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100091a050] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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59
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Rowntree P, Parenteau L, Sanche L. Dielectric polarization invariance in dissociative electron attachment from condensed saturated hydrocarbons. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100155a008] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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60
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Lu QB, Bass AD, Sanche L. Superinelastic electron transfer: electron trapping in H2O ice via the N-2((2)Pi(g)) resonance. PHYSICAL REVIEW LETTERS 2002; 88:147601. [PMID: 11955176 DOI: 10.1103/physrevlett.88.147601] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2001] [Indexed: 05/23/2023]
Abstract
We present measurements on the trapping of 0-3 eV electrons in H2O ice films covered with a submonolayer of N2 molecules. At the energy of the N-2((2)Pi(g)) shape resonance, the absolute cross section for electron trapping in ice is approximately 5.5 x 10(-16) cm(2), similar to that for vibrational excitations of gaseous N2 via the resonance. This result, indicating that nearly all electrons from autoionization of N-2((2)Pi(g)) are transferred to electron traps in ice, is explained by superinelastic electron transfer from N-2((2)Pi(g)) into preexisting traps in polar ice, leaving N2 in high vibrational excited states.
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Abstract
We report direct measurements of the formation of single-, double- and multiple strand breaks in pure plasmid DNA as a function of exposure to 10-50 eV electrons. The effective cross sections to produce these different types of DNA strand breaks were determined and were found to range from approximately 10(-17) to 3 x 10(-15) cm(2). The total effective cross section and the effective range for destruction of supercoiled DNA extend from 3.4 to 4.4 x 10(-15) cm(2) and 12 to 14 nm, respectively, over the range 10-50 eV. The variation of the effective cross sections with electron energy is discussed in terms of the electron's inelastic mean free path, penetration depth, and dissociation mechanisms, including resonant electron capture; the latter is found to dominate the effective cross sections for single- and double-strand breaks at 10 eV. The most striking observations are that (1) supercoiled DNA is approximately one order of magnitude more sensitive to the formation of double-strand breaks by low-energy electrons than is relaxed circular DNA, and (2) the dependence of the effective cross sections on the incident electron energy is unrelated to the corresponding ionization cross sections. This finding suggests that the traditional notion that radiobiological damage is related to the number of ionization events would not apply at very low energies.
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Abdoul-Carime H, Sanche L. Fragmentation of short single DNA strands by 1-30 eV electrons: dependence on base identity and sequence. Int J Radiat Biol 2002; 78:89-99. [PMID: 11779359 DOI: 10.1080/09553000110090016] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
PURPOSE To investigate the dependence of base identity and sequence on the damage induced by low-energy (1-30 eV) electron impact on a short single strand of DNA. MATERIALS AND METHODS Monolayers of homogeneous nonamers of deoxycytidine and thymidine (dCy9 and T9) and heterogeneous nonamers of thymidine substituted with 33 and 66% of deoxycytidine (dCy3-T6 and dCy6-T3) were chemisorbed onto a gold substrate. They were bombarded under ultrahigh vacuum conditions by a 1-30 eV electron beam. Neutral fragments desorbed from the films were detected by a mass spectrometer. From partial pressure measurements, the effective cross-section (ECS) per base for desorption of various fragments was estimated. RESULTS CN, OCN and/or H2NCN were the major neutral species observed to desorb in the present experiments. A small contribution of 55 amu neutral species, tentatively attributed to CH3CCO, were only detected from fragmentation of oligonucleotides containing thymine. The total ECS per base estimated for the CN, OCN and CH3CCO species production from fragmentation of dCy9, dCy6-T3, dCy3-T6 and T9 at 12 eV incident electron energy were (3.4, 2.0, 2.9 and 2.3) x 10(-17) cm(2), respectively. The incident electron energy dependence of ECS for desorption of these fragments exhibited structures <20 eV, which are characteristic of transient anion formation. CONCLUSIONS At incident electron energies <20 eV, neutral fragment desorption arise from dissociation of the DNA bases, principally via dissociative electron attachment and/or decay of the transient anion into a dissociative electronic excited state of the base. Non-resonant mechanisms (e.g. direct dipolar dissociation) mostly control the fragmentation processes >20 eV. From comparison of the electron energy dependence of the ECS for base fragmentation in the homo- and heteronucleotides, it is concluded that damage to a short DNA strand is dependent on base identity, sequence and electron energy.
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Sanche L. Mechanisms of low energy electron damage to condensed biomolecules and DNA. RADIATION PROTECTION DOSIMETRY 2002; 99:57-62. [PMID: 12194361 DOI: 10.1093/oxfordjournals.rpd.a006839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It has recently been shown that 3-20 eV electron impact on vacuum-dry samples of plasmid DNA induced substantial yields of single and double strand breaks (SSBs and DSBs). These results are summarised in the present article along with those obtained from the fragmentation of elementary components (i.e. condensed H2O, bases and sugar analogues) of DNA induced by low energy electron impact under ultra high vacuum conditions. By comparing the results from these experiments, it is possible to determine fundamental mechanisms by which low energy electrons damage DNA. The decay of transient anions formed on the DNA's basic components is found to play a crucial role in producing SSBs and DSBs. Since a large portion of the energy deposited by ionising radiation first leads to the production of low energy secondary electrons, these findings provide basic knowledge necessary to understand the genotoxic effects of high energy radiation and eventually modify these effects at the molecular level.
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Lu QB, Sanche L. Large enhancement in dissociative electron attachment to HCl adsorbed on H2O ice via transfer of presolvated electrons. J Chem Phys 2001. [DOI: 10.1063/1.1406499] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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65
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Bass AD, Parenteau L, Weik F, Sanche L. Effects of morphology on the low-energy electron stimulated desorption of O− from O2 deposited on benzene and water ices. J Chem Phys 2001. [DOI: 10.1063/1.1394733] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
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66
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Lu QB, Sanche L. Effects of cosmic rays on atmospheric chlorofluorocarbon dissociation and ozone depletion. PHYSICAL REVIEW LETTERS 2001; 87:078501. [PMID: 11497927 DOI: 10.1103/physrevlett.87.078501] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2001] [Indexed: 05/23/2023]
Abstract
Data from satellite, balloon, and ground-station measurements show that ozone loss is strongly correlated with cosmic-ray ionization-rate variations with altitude, latitude, and time. Moreover, our laboratory data indicate that the dissociation induced by cosmic rays for CF(2)Cl(2) and CFCl(3) on ice surfaces in the polar stratosphere at an altitude of approximately 15 km is quite efficient, with estimated rates of 4.3 x 10(-5) and 3.6 x 10(-4) s(-1), respectively. These findings suggest that dissociation of chlorofluorocarbons by capture of electrons produced by cosmic rays and localized in polar stratospheric cloud ice may play a significant role in causing the ozone hole.
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Abstract
The ability of low-energy electrons to induce single- and double-strand breaks in DNA has recently been demonstrated. Here we show the propensity of 3-30 eV electrons to initiate base sequence-dependent damage to a short single DNA strand. Solid monolayer films of homogeneous thymidine (T(9)) and deoxycytidine (dCy(9)) and heterogeneous oligomers (T(6)dCy(3)) are bombarded with 1-30 eV electrons in an ultrahigh-vacuum system. CN, OCN and/or H(2)NCN are detected by a mass spectrometer as the most intense neutral fragments desorbing in vacuum. A weaker signal of CH(3)CCO is also detected, but only from oligonucleotides containing thymine. Below 17 eV, the energy dependence of the yields of CN, OCN and CH(3)CCO exhibits resonance-like structures, attributed to dissociative electron attachment (DEA). Above 17 eV, the monotonic increase in the fragment yields indicates that nonresonant processes (i.e. dipolar dissociation) control the fragmentation of these molecules. Within the energy range investigated, comparison of the magnitude of the total fragment yields produced by electron attack on dCy(9), T(6)-dCy(3) and T(9) suggests the following order in the sensitivity of single-strand DNA: dCy(9) > T(6)-dCy(3) > T(9). At 12 eV, the total fragment yields are found to be 5.8, 5.0 and 3.9 x 10(-3) fragment/electron, respectively. From the yields obtained with the two homo-oligonucleotides, we differentiate between contributions arising from the chemical nature of the base and the effect of environment (i.e. the sequence) when a thymidine unit in T(9) is replaced by dCy. The base sequence-dependent damage is found to vary with incident electron energy. These results reinforce the idea that genomic sensitivity to ionizing radiation depends on local genetic information. Furthermore, they underscore the possible role of low-energy electrons in the pathways responsible for the induction of specific genomic lesions.
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Lu QB, Madey TE, Parenteau L, Weik F, Sanche L. Structural and temperature effects on Cl− yields in electron-induced dissociation of CF2Cl2 adsorbed on water ice. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00569-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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69
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Abdoul-Carime H, Huels MA, Illenberger E, Sanche L. Sensitizing DNA to secondary electron damage: resonant formation of oxidative radicals from 5-halouracils. J Am Chem Soc 2001; 123:5354-5. [PMID: 11457401 DOI: 10.1021/ja003952d] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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70
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Abdoul-Carime H, Cloutier P, Sanche L. Low-energy (5-40 eV) electron-stimulated desorption of anions from physisorbed DNA bases. Radiat Res 2001; 155:625-33. [PMID: 11260665 DOI: 10.1667/0033-7587(2001)155[0625:leeesd]2.0.co;2] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We present the results of experiments on anion desorption from the physisorbed DNA bases adenine, thymine, guanine and cytosine induced by the impact of low-energy (5-40 eV) electrons. Electron bombardment of DNA base films induces ring fragmentation and desorption of H(-), O(-), OH(-), CN(-), OCN(- ) and CH(2)(-) anions through either single or complex multibond dissociation. We designate the variation of the yield of an anion with electron energy as the yield function. Below 15 eV incident electron energy, bond cleavage is controlled mainly by dissociative electron attachment. Above 15 eV, the portion of a yield function that increases linearly is attributed to nonresonant processes, such as dipolar dissociation. A resonant structure is superimposed on this signal around 20 eV in the anion yield functions. This structure implicates dissociative electron attachment and/or resonant decay of the transient anion into the dipolar dissociation channel, with a minimal contribution from multiple inelastic electron scattering. The yields of all desorbing anions clearly show that electron resonances contribute to the damage of all DNA bases bombarded with 5-40 eV electrons. Comparison of the ion yields indicates that adenine is the least sensitive base to slow electron attack. Electron-irradiated guanine films exhibit the largest yields of desorbed anions.
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Nagesha K, Fabrikant II, Sanche L. Electron attachment to CF3Cl and CH3Cl on the surface and in the bulk of solid Kr. J Chem Phys 2001. [DOI: 10.1063/1.1347964] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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72
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Sanche L. Interaction of 0-15 eV electrons with molecular solids: formation of charged excitonic complexes. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/13/25/003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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73
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Bass AD, Parenteau L, Weik F, Sanche L. The effects of temperature and morphology on electron transmission and stimulated desorption of H− from thin hydrocarbon films. J Chem Phys 2000. [DOI: 10.1063/1.1318200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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74
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Vichnevetski E, Bass AD, Sanche L. Sample morphology and porosity in electron stimulated desorption: N2* from N2 adsorbed onto nanoscale ice films. J Chem Phys 2000. [DOI: 10.1063/1.1288029] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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75
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Boudaïffa B, Hunting D, Cloutier P, Huels MA, Sanche L. Induction of single- and double-strand breaks in plasmid DNA by 100-1500 eV electrons. Int J Radiat Biol 2000; 76:1209-21. [PMID: 10993632 DOI: 10.1080/09553000050134447] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
PURPOSE To investigate the induction of DNA strand breaks by electrons with energies ranging from 0.1 to 1.5 keV. MATERIALS AND METHODS Dry supercoiled plasmid DNA was irradiated with electrons of energies ranging from 0.1 to 1.5 keV and the results were compared with those obtained by gamma-irradiation of the same plasmid in solution. For electron irradiation, the plasmid was deposited on a gold substrate under a controlled atmosphere to minimize contamination of the DNA film. Electron bombardments were performed under ultra-high vacuum conditions (UHV 10(-9) torr). DNA damage was detected by gel electrophoresis followed by quantitation of the DNA bands by fluorescence or by hybridization with a radioactive probe. RESULTS Electrons with energies from 0.1 to 1.5 keV induced single, double and multiple double-strand breaks in supercoiled plasmid DNA. For equal doses, we observed a marked increase in the efficiency of induction of double- and multiple-strand breaks in supercoiled DNA as a function of electron energy. In contrast to gamma-irradiation, the formation of small DNA fragments by electrons did not seem to be related to the production of the linear form of the plasmid. CONCLUSIONS Electrons within the energy; range of the secondary electrons generated by high-energy ionizing radiation induce single, double and multiple double-strand breaks in DNA. Problems associated with low-energy electron irradiation experiments and dose calculations in thin films are also discussed.
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