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Liu C, Zheng Y, Sanche L. Damage Induced to DNA and Its Constituents by 0-3 eV UV Photoelectrons †. Photochem Photobiol 2021; 98:546-563. [PMID: 34767635 DOI: 10.1111/php.13559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 11/07/2021] [Indexed: 11/28/2022]
Abstract
The complex physical and chemical interactions between DNA and 0-3 eV electrons released by UV photoionization can lead to the formation of various lesions such as base modifications and cleavage, crosslinks and single strand breaks. Furthermore, in the presence of platinum chemotherapeutic agents, these electrons can cause clustered lesions, including double strand breaks. We explain the mechanisms responsible for these damages via the production 0-3 eV electrons by UVC radiation, and by UV photons of any wavelengths, when they are produced by photoemission from nanoparticles lying within about 10 nm from DNA. We review experimental evidence showing that a single 0-3 eV electron can produce these damages. The foreseen benefits UV-irradiation of nanoparticles targeted to the cell nucleus are mentioned in the context of cancer therapy, as well as the potential hazards to human health when they are present in cells.
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Affiliation(s)
- Chaochao Liu
- State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou, China
| | - Yi Zheng
- State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou, China
| | - Léon Sanche
- Département de Médecine Nucléaire et Radiobiologie et Centre de Recherche Clinique, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, Canada
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2
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Jensen ET. Contrasting mechanisms for photodissociation of methyl halides adsorbed on thin films of C 6H 6 and C 6F 6. Phys Chem Chem Phys 2021; 23:3748-3760. [PMID: 33533786 DOI: 10.1039/d0cp05844k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanisms for photodissociation of methyl halides (CH3X, X = Cl, Br, I) have been studied for these molecules when adsorbed on thin films of C6H6 or C6F6 on copper single crystals, using time-of-flight spectroscopy with 248 nm and 193 nm light. For CH3Cl and CH3Br monolayers adsorbed on C6H6, two photodissociation pathways can be identified - neutral photodissociation similar to the gas-phase, and a dissociative electron attachment (DEA) pathway due to photoelectrons from the metal. The same methyl halides adsorbed on a C6F6 thin film display only neutral photodissociation, with the DEA pathway entirely absent due to intermolecular quenching via a LUMO-derived electronic band in the C6F6 thin film. For CH3I adsorbed on a C6F6 thin film, illumination with 248 nm light results in CH3 photofragments departing due to neutral photodissociation via the A-band absorption. When CH3I monolayers on C6H6 thin films are illuminated at the same wavelength, additional new photodissociation pathways are observed that are due to absorption in the molecular film with energy transfer leading to dissociation of the CH3I molecules adsorbed on top. The proposed mechanism for this photodissociation is via a charge-transfer complex for the C6H6 layer and adsorbed CH3I.
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Affiliation(s)
- E T Jensen
- Department of Physics, University of Northern BC, 3333 University Way, Prince George B.C., V2N 4Z9, Canada.
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Pshenichnyuk SA, Modelli A, Komolov AS. Interconnections between dissociative electron attachment and electron-driven biological processes. INT REV PHYS CHEM 2018. [DOI: 10.1080/0144235x.2018.1461347] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Stanislav A. Pshenichnyuk
- Institute of Molecule and Crystal Physics – Subdivision of the Ufa Research Centre of the Russian Academy of Sciences, Ufa, Russia
| | - Alberto Modelli
- Dipartimento di Chimica ‘G. Ciamician’, Università di Bologna, Bologna, Italy
- Centro Interdipartimentale di Ricerca in Scienze Ambientali, Ravenna, Italy
| | - Alexei S. Komolov
- Department of Solid State Electronics, St. Petersburg State University, St. Petersburg, Russia
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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] [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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Pshenichnyuk SA, Komolov AS. Why Can Unnatural Electron Acceptors Protect Photosynthesizing Organisms but Kill the Others? J Phys Chem B 2017; 121:749-757. [DOI: 10.1021/acs.jpcb.6b12007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stanislav A. Pshenichnyuk
- Institute
of Molecule and Crystal Physics, Ufa Research Centre, Russian Academy of Sciences, Prospeκt Oktyabrya 151, 450075 Ufa, Russia
- St. Petersburg State University, Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia
| | - Alexei S. Komolov
- St. Petersburg State University, Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia
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6
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Jensen ET. Excitation and quenching mechanisms in the near-UV photodissociation of CH3Br and CH3Cl adsorbed on D2O or CH3OH on Cu(110). Phys Chem Chem Phys 2015; 17:9173-85. [PMID: 25757378 DOI: 10.1039/c4cp06128d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photochemical processes for CH3X (X = Cl, Br, I) adsorbed on top of thin films of D2O or CH3OH on a Cu(110) substrate is studied by time-of-flight mass spectrometry for a range of UV wavelengths (351-193 nm). Photodissociation via dissociative electron attachment by photoelectrons and by neutral photodissociation is identified and quantified based on the observed dynamics of the desorbing CH3 fragments. Photoelectron-driven dissociation of CH3X is found to be a maximum for monolayer quantities of the D2O or CH3OH on Cu(110), but with differing kinetic energy release on the two substrates. The dynamics of CH3Br and CH3Cl photodissociation qualitatively differ on CH3OH/Cu(110) as compared to D2O/Cu(110), which is ascribed to differing molecular structures for these systems. Evidence is presented for an efficient inter-molecular quenching mechanism for neutral photoexcitation of CH3Cl and CH3Br on the CH3OH/Cu(110) substrate.
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Affiliation(s)
- E T Jensen
- Department of Physics, University of Northern BC, 3333 University, Way, Prince George B.C., V2N 4Z9, Canada.
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Horowitz Y, Asscher M. Electron-induced chemistry of methyl chloride caged within amorphous solid water. J Chem Phys 2013; 139:154707. [PMID: 24160533 DOI: 10.1063/1.4824385] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The interaction of low energy electrons (1.0-25 eV) with methyl-chloride (CD3Cl) molecules, caged within Amorphous Solid Water (ASW) films, 10-120 monolayer (ML) thick, has been studied on top of a Ru(0001) substrate under Ultra High Vacuum (UHV) conditions. While exposing the ASW film to 3 eV electrons a static electric field up to 8 × 10(8) V∕m is developed inside the ASW film due to the accumulation of trapped electrons that produce a plate capacitor voltage of exactly 3 V. At the same time while the electrons continuously strike the ASW surface, they are transmitted through the ASW film at currents of ca. 3 × 10(-7) A. These electrons transiently attach to the caged CD3Cl molecules leading to C-Cl bond scission via Dissociative Electron Attachment (DEA) process. The electron induced dissociation cross sections and product formation rate constants at 3.0 eV incident electrons at ASW film thicknesses of 10 ML and 40 ML were derived from model simulations supported by Thermal Programmed Desorption (TPD) experimental data. For 3.0 eV electrons the CD3Cl dissociation cross section is 3.5 × 10(-16) cm(2), regardless of ASW film thickness. TPD measurements reveal that the primary product is deuterated methane (D3CH) and the minor one is deuterated ethane (C2D6).
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Affiliation(s)
- Yonatan Horowitz
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmund J. Safra Campus, Givat-Ram, Jerusalem 91904, Israel
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Miller ER, Muirhead GD, Jensen ET. Mechanisms for the near-UV photodissociation of CH3I on D2O/Cu(110). J Chem Phys 2013; 138:084702. [DOI: 10.1063/1.4770225] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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9
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Mirsaleh-Kohan N, Bass AD, Sanche L. Effect of morphology of thin DNA films on the electron stimulated desorption of anions. J Chem Phys 2011; 134:015102. [PMID: 21219028 PMCID: PMC3217040 DOI: 10.1063/1.3520562] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We present a comparison between the electron stimulated desorption (ESD) of anions from DNA samples prepared by lyophilization (an example of poorly organized or nonuniform films) and molecular self-assembly (well-ordered films). The lyophilization (or freeze- drying) method is perhaps the most frequently employed technique for forming DNA films for studies of low-energy electron (LEE) interactions leading to DNA damage; however, this technique usually produces nonuniform films with considerable clustering which may affect DNA configuration and enhance sample charging when the film is irradiated. Our results confirm the general validity of ESD measurements obtained with lyophilized samples, but also reveal limitations of lyophilization for LEE studies on DNA films. Specifically we observe some modulation of structures, associated with dissociative electron attachment, in the anion yield functions from different types of DNA film, confirming that conformational factors play a role in the LEE induced damage to DNA.
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Affiliation(s)
- Nasrin Mirsaleh-Kohan
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et les Sciences de Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
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Zheng Y, Sanche L. Influence of organic ions on DNA damage induced by 1 eV to 60 keV electrons. J Chem Phys 2010; 133:155102. [PMID: 20969428 PMCID: PMC3217039 DOI: 10.1063/1.3505046] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report the results of a study on the influence of organic salts on the induction of single strand breaks (SSBs) and double strand breaks (DSBs) in DNA by electrons of 1 eV to 60 keV. Plasmid DNA films are prepared with two different concentrations of organic salts, by varying the amount of the TE buffer (Tris-HCl and EDTA) in the films with ratio of 1:1 and 6:1 Tris ions to DNA nucleotide. The films are bombarded with electrons of 1, 10, 100, and 60 000 eV under vacuum. The damage to the 3197 base-pair plasmid is analyzed ex vacuo by agarose gel electrophoresis. The highest yields are reached at 100 eV and the lowest ones at 60 keV. The ratios of SSB to DSB are surprisingly low at 10 eV (∼4.3) at both salt concentrations, and comparable to the ratios measured with 100 eV electrons. At all characteristic electron energies, the yields of SSB and DSB are found to be higher for the DNA having the lowest salt concentration. However, the organic salts are more efficient at protecting DNA against the damage induced by 1 and 10 eV electrons. DNA damage and protection by organic ions are discussed in terms of mechanisms operative at each electron energy. It is suggested that these ions create additional electric fields within the groove of DNA, which modify the resonance parameter of 1 and 10 eV electrons, namely, by reducing the electron capture cross-section of basic DNA units and the lifetime of corresponding transient anions. An interstrand electron transfer mechanism is proposed to explain the low ratios for the yields of SSB to those of DSB produced by 10 eV electrons.
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Affiliation(s)
- Yi Zheng
- Research Institute of Photocatalysis, Fuzhou University, Fuzhou 35002, People's Republic of China.
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11
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Kokh DB, Liebermann HP, Buenker RJ. Photodissociation of CH3Cl, C2H5Cl, and C6H5Cl on the Ag(111) surface:Ab initioembedded cluster and configuration interaction study. J Chem Phys 2010; 132:074707. [DOI: 10.1063/1.3322289] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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13
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Jensen ET. Charge-transfer photodissociation of adsorbed molecules via electron image states. J Chem Phys 2008; 128:044301. [DOI: 10.1063/1.2822331] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Perry CC, Faradzhev NS, Madey TE, Fairbrother DH. Electron stimulated reactions of methyl iodide coadsorbed with amorphous solid water. J Chem Phys 2007; 126:204701. [PMID: 17552783 DOI: 10.1063/1.2722749] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The electron stimulated reactions of methyl iodide (MeI) adsorbed on and suspended within amorphous solid water (ice) were studied using a combination of postirradiation temperature programmed desorption and reflection absorption infrared spectroscopy. For MeI adsorbed on top of amorphous solid water (ice), electron beam irradiation is responsible for both structural and chemical transformations within the overlayer. Electron stimulated reactions of MeI result principally in the formation of methyl radicals and solvated iodide anions. The cross section for electron stimulated decomposition of MeI is comparable to the gas phase value and is only weakly dependent upon the local environment. For both adsorbed MeI and suspended MeI, reactions of methyl radicals within MeI clusters lead to the formation of ethane, ethyl iodide, and diiodomethane. In contrast, reactions between the products of methyl iodide and water dissociation are responsible for the formation of methanol and carbon dioxide. Methane, formed as a result of reactions between methyl radicals and either parent MeI molecules or hydrogen atoms, is also observed. The product distribution is found to depend on the film's initial chemical composition as well as the electron fluence. Results from this study highlight the similarities in the carbon-containing products formed when monohalomethanes coadsorbed with amorphous solid water are irradiated by either electrons or photons.
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Affiliation(s)
- C C Perry
- Department of Chemistry, Oakwood College, Huntsville, Alabama 35896, USA
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15
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Naaman R, Sanche L. Low-Energy Electron Transmission through Thin-Film Molecular and Biomolecular Solids. Chem Rev 2007; 107:1553-79. [PMID: 17439288 DOI: 10.1021/cr040200j] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R Naaman
- Department of Chemical Physics, Weizmann Institute, Rehovot, Israel 76100
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Osgood R. Photoreaction Dynamics of Molecular Adsorbates on Semiconductor and Oxide Surfaces. Chem Rev 2006; 106:4379-401. [PMID: 17031991 DOI: 10.1021/cr050175x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard Osgood
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
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Camillone N, Pak TR, Adib K, Osgood RM. Tuning Molecule−Surface Interactions with Sub-Nanometer-Thick Covalently Bound Organic Monolayers. J Phys Chem B 2006; 110:11334-43. [PMID: 16771404 DOI: 10.1021/jp0606659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Measurements of the thermal desorption of methyl bromide (MeBr) from bare and RS-functionalized GaAs(110), where R = CH3 and CH3CH2, reveal marked systematic changes in molecule-surface interactions. As the thickness of the organic spacer layer is increased, the electrostatic MeBr-GaAs(110) interaction decreases, lowering the activation energy for desorption, Ed, as well as decreasing the critical coverage required for nucleation of bulklike MeBr. On the CH3CH2S-functionalized surface, Ed is lowered to a value roughly equal to that for desorption from three-dimensional (3-D) clusters; because the kinetics of desorption of isolated molecules differs from that for desorption from clusters, desorption of isolated molecules from the organic surface occurs at a lower temperature than desorption from the clusters. Thus, the "monolayer" desorption wave occurs at a lower temperature than the "multilayer" desorption wave. These results illustrate the role that organic chain length in nanometer-scale thin films can play in alteration of the delicate balance of interfacial interactions.
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Affiliation(s)
- Nicholas Camillone
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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Mozejko P, Bass AD, Parenteau L, Sanche L. Intrinsic and extrinsic factors in anion electron-stimulated desorption: D− from deuterated hydrocarbons condensed on Kr and water ice films. J Chem Phys 2004; 121:10181-9. [PMID: 15549893 DOI: 10.1063/1.1807813] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The results of D(-) ion desorption induced by 3-20 eV electrons incident on condensed CD(4), C(2)D(6), C(3)D(8), C(2)D(4), and C(2)D(2) are presented. These compounds were deposited in submonolayer amounts on the surfaces of multilayer solid films of Kr and nonporous and porous amorphous ice. While desorption of the D(-) anions proceeds via well-known processes, i.e., dissociative electron attachment (DEA) and dipolar dissociation, significant perturbations of these processes due to presence of the different film substrates are observed. We have shown that it is possible to distinguish between the character and nature of these perturbations. The presence of the nonporous ice perturbs the D(-) desorption intensity by affecting the intrinsic properties of the intermediate anion states through which dissociation proceeds. On the other hand, the presence of the porous ice introduces extrinsic effects, which can affect electron energy losses prior to their interaction with the hydrocarbon molecule and/or the energies and intensities of the fragment species after dissociation. Simple mechanisms responsible for the observed variations in the intensities of desorbed anionic signals are proposed and discussed. Electron transfer from transient anion states to electron states of the substrate film or nearby hydrocarbon molecules appear as the most efficient mechanism to reduce the magnitude of the DEA process.
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Affiliation(s)
- Paweł Mozejko
- Groupe en Sciences des Radiations, Faculté de Medecine, Université de Sherbrooke, Sherbrooke, Québec J1H5N4 Canada.
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Srivastava A, Osgood RM. State-resolved dynamics of 248 nm methyl-iodide fragmentation on GaAs(110). J Chem Phys 2003. [DOI: 10.1063/1.1619944] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Livneh T, Asscher M. Photoinduced Fragmentation of Multilayer CH3Br on Cu/Ru(001). J Phys Chem B 2003. [DOI: 10.1021/jp027857y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tsachi Livneh
- Department of Physical Chemistry, Nuclear Research Center, Negev, P.O. Box 9001 Beer-Sheva 84190, Israel, and Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel
| | - Micha Asscher
- Department of Physical Chemistry, Nuclear Research Center, Negev, P.O. Box 9001 Beer-Sheva 84190, Israel, and Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew University, Jerusalem 91904, Israel
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21
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Srivastava A, Osgood RM. Photoreaction dynamics of CH3I multilayers on GaAs(110): REMPI probing of the CH3 umbrella mode. Chem Phys Lett 2002. [DOI: 10.1016/s0009-2614(02)00287-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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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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Affiliation(s)
- B Boudaïffa
- Group of the Canadian Institutes of Health Research in the Radiation Sciences, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, University of Sherbrooke, 3001, 12th Avenue North, Sherbrooke, Quebec, Canada J1H 5N4
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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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Affiliation(s)
- H Abdoul-Carime
- Groupe des Institutes Canadiens de Recherches en Santé en Sciences des Radiations, Département de Médecine Nucléaire et de Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Camillone N, Khan KA, Yarmoff JA, Osgood RM. Surface-reconstruction-switched adsorbate photofragmentation dynamics. PHYSICAL REVIEW LETTERS 2001; 87:056101. [PMID: 11497789 DOI: 10.1103/physrevlett.87.056101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2000] [Indexed: 05/23/2023]
Abstract
Energy-resolved angular distributions of neutral fragments ejected during photoinduced electron transfer reaction of CH3Br on GaAs(100) exhibit three distinct methyl-radical ejection channels. These undergo marked changes when the termination is switched from the Ga-rich c(8 x 2) to the As-rich c(2 x 8). Our observations are consistent with a strong adsorption-site dependence of the dynamics.
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Affiliation(s)
- N Camillone
- Columbia Radiation Laboratory, Columbia University, New York, New York 10027, USA.
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Chen JM, Lu KT. State-specific enhancement of Cl+ and Cl- desorption for SiCl4 adsorbed on a Si(100) surface following Cl 2 p and Si 2 p core-level excitations. PHYSICAL REVIEW LETTERS 2001; 86:3176-3179. [PMID: 11290136 DOI: 10.1103/physrevlett.86.3176] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2000] [Indexed: 05/23/2023]
Abstract
State-specific desorption for SiCl4 adsorbed on a Si(100) surface at approximately 90 K with variable coverage following the Cl 2p and Si 2p core-level excitations has been investigated using synchrotron radiation. The Cl+ yields show a significant enhancement following the Cl 2p-->8a*1 excitation. The Cl- yields are notably enhanced at the 8a*1 resonance at both Cl 2p and Si 2p edges. The enhancement of the Cl- yield occurs through the formation of highly excited states of the adsorbed molecules. These results provide some new dissociation processes from adsorbates on surfaces via core-level excitation.
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Affiliation(s)
- J M Chen
- Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan, Republic of China
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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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Lourenço J, Carrapa R, Teodoro O, Moutinho A, Gleeson M, Los J, Kleyn A. Positive and negative ion emission from perfluorinated poly-ethers. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00119-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Johnson CC, Jensen ET. Photolysis of CH3I on Cu(110) at 337 nm: Direct and charge-transfer photodissociation. J Chem Phys 2000. [DOI: 10.1063/1.481165] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Lu PH, Polanyi JC, Rogers D. Electron-induced “localized atomic reaction” (LAR): Chlorobenzene adsorbed on Si(111) 7×7. J Chem Phys 1999. [DOI: 10.1063/1.480325] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Khrapak AG, Tegeder P, Illenberger E, Schmidt WF. The energy of a negative ion in a non-polar liquid. Chem Phys Lett 1999. [DOI: 10.1016/s0009-2614(99)00747-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Khan KA, Camillone N, Osgood RM. Chain-Length Dependence of the Dissociation Dynamics of Oriented Molecular Adsorbates: n-Alkyl Bromides on GaAs(110). J Phys Chem B 1999. [DOI: 10.1021/jp990782m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Khalid A. Khan
- Columbia Radiation Laboratory, Columbia University, New York, New York 10027
| | - Nicholas Camillone
- Columbia Radiation Laboratory, Columbia University, New York, New York 10027
| | - Richard M. Osgood
- Columbia Radiation Laboratory, Columbia University, New York, New York 10027
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Khan KA, Camillone N, Osgood RM. Photoinitiated electron transfer to selected physisorbed alkyl bromides: The effects of alkyl chain length on dissociation cross sections. J Chem Phys 1999. [DOI: 10.1063/1.478984] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Camillone N, Khan KA, Lasky PJ, Wu L, Moryl JE, Osgood RM. The wavelength dependence of photoinduced hot electron dissociative attachment to methyl bromide adsorbed on gallium arsenide (110). J Chem Phys 1998. [DOI: 10.1063/1.476970] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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White J. Using photons and electrons to drive surface chemical reactions1Dedicated to the memory of Brian Bent whose work stimulated much of our own and whose pleasant encouragement never failed.1. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s1381-1169(97)00257-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Weik F, Illenberger E, Nagesha K, Sanche L. Dissociative Electron Attachment to Gas- and Condensed-Phase CF3Cl: Anion Desorption and Trapping. J Phys Chem B 1998. [DOI: 10.1021/jp972535t] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Huels MA, Hahndorf I, Illenberger E, Sanche L. Resonant dissociation of DNA bases by subionization electrons. J Chem Phys 1998. [DOI: 10.1063/1.475503] [Citation(s) in RCA: 224] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Skowronek S, Pereira R, González Ureña A. Spectroscopy and Dynamics of Excited Harpooning Reactions: The Photodepletion Action Spectrum of the Ba···FCH3 Complex. J Phys Chem A 1997. [DOI: 10.1021/jp970385g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. Skowronek
- Unidad de Laseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Juan XXIII, 1, 28040 Madrid, Spain
| | - R. Pereira
- Unidad de Laseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Juan XXIII, 1, 28040 Madrid, Spain
| | - A. González Ureña
- Unidad de Laseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Juan XXIII, 1, 28040 Madrid, Spain
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