Dissociative electron attachment in nanoscale ice films: Thickness and charge trapping effects

Simpson, W. C.; Orlando, Thomas M.; Parenteau, L.; Nagesha, K.; Sanche, Léon

doi:10.1063/1.475924

Cited by 80 publications

(75 citation statements)

References 48 publications

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“…This phenomenon is akin to an attenuation length (AL) for the incident LEEs inside the film and thus limits the LEEinduced damage to a fraction of the film. Besides, most of the LEEs suffer energy loss inside the DNA molecules and end up in intermolecular traps, or via dissociative electron attachment (DEA) stabilize as atomic or molecular anions leading to film charging [50][51][52][53][54]. Both AL and film charging effects can lead to considerable error in the CS values for the formation of DNA damage if not accounted for in the data analysis.…”

Section: Introductionmentioning

confidence: 99%

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

et al. 2012

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Cross sections (CSs) for the interaction of low-energy electrons (LEE) with condensed macromolecules are essential parameters for accurate modeling of radiation-induced molecular decomposition and chemical synthesis. Electron irradiation of dry nanometer-scale macromolecular solid films has often been employed to measure CSs and other quantitative parameters for LEE interactions. Since such films have thicknesses comparable with electron thermalization distances, energy deposition varies throughout the film. Moreover, charge accumulation occurring inside the films shields a proportion of the macromolecules from electron irradiation. Such effects complicate the quantitative comparison of the CSs obtained in films of different thicknesses and limit the applicability of such measurements. Here, we develop a simple mathematical model, termed the molecular survival model, that employs a CS for a particular damage process together with an attenuation length related to the total CS, to investigate how a measured CS might be expected to vary with experimental conditions. As a case study, we measure the absolute CS for the formation of DNA strand breaks (SBs) by electron irradiation at 10 and 100 eV of lyophilized plasmid DNA films with thicknesses between 10 and 30 nm. The measurements are shown to depend strongly on the thickness and charging condition of the nanometer-scale films. Such behaviors are in accord with the model and support its validity. Via this analysis, the CS obtained for SB damage is nearly independent of film thickness and charging effects. In principle, this model can be adapted to provide absolute CSs for electron-induced damage or reactions occurring in other molecular solids across a wider range of experimental conditions.

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Section: Introductionmentioning

confidence: 99%

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

et al. 2012

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“…The return of secondary electrons to a positively charged surface can have significant effects in the sputtering of insulators [2]. Limited laboratory studies have focused on the charging of ice films due to charge imbalance upon ion [3] or electron [4,5] injection. Other research has examined the simpler case of charging and breakdown in rare gas solids.…”

Section: Introductionmentioning

confidence: 99%

Ion-induced electrostatic charging of ice at 15–160 K

et al. 2012

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We studied electrostatic charging of ice films induced by the impact of 1-200 keV Ar + ions and their subsequent discharging post-irradiation. We derived the positive surface electrostatic potential from the kinetic energy of sputtered molecular ions and with a Kelvin probe. Measurements were performed as a function of film thickness, temperature and ion energy. Charging requires that the projectile ions are stopped in the ice and that the ice temperature is below 160 K. The decay of the electrostatic charge after irradiation is determined by two time constants, corresponding to the detrapping of trapped charges in shallow and deep traps within the ice. Amorphous solid water films are found to charge to a higher electrostatic potential than crystalline ice films. The surface potential of crystalline ice increases and decreases during cooling and warming, respectively, without hysteresis. We present a model to describe the charging and discharging processes.

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“…The oligonucleotides were embedded into multilayer films of amorphous ice to simulate the water molecules surrounding cellular DNA. 17,18,19 The presence of water around DNA was found to modify the TNI manifold, the corresponding decay channels and thus the SSB and DSB yield functions. 20,21 More recently, theoretical studies indicated that the solvation of DNA molecules (i.e., immersion in an environment of polar molecules such as water) could significantly increase their ability to capture electrons with energies near zero or lower, via the modification of adiabatic electron affinity of solvated DNA bases in bulk water.…”

Section: Introductionmentioning

confidence: 99%

Radiation Damage to DNA: The Indirect Effect of Low-Energy Electrons

Alizadeh

Sanz²,

Garcia³

et al. 2013

J. Phys. Chem. Lett.

113

103

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We report the effect of DNA hydration level on damage yields induced by soft X-rays and photoemitted low energy electrons (LEEs) in thin films of plasmid DNA irradiated in N 2 at atmospheric pressure under different humidity levels. Contrary to a dilute solution of DNA, the number of H 2 O molecules per nucleotide (Γ) in these films can be varied from Γ=2.5 to ~33, where Γ≤20 corresponds to layers of hydration and Γ=33 to an additional bulk-like water layer. Our results indicate that DNA damage induced by LEEs does not increase significantly until the second hydration shell is formed. However, this damage increases dramatically as DNA coverage approaches bulk-like hydration conditions. A number of phenomena are invoked to account for these behaviors including: dissociative electron transfer from water-interface electron traps to CIHR Author Manuscript CIHR Author Manuscript CIHR Author ManuscriptDNA bases, quenching of dissociative electron attachment to DNA and quenching of dissociative electronically excited states of H 2 O in contact with DNA. KeywordsDNA damage; strand breaks; humidity level; solvation; interface electronThe discovery that low energy electrons (LEEs, E<30 eV) can directly damage the DNA molecule with considerable efficiency 1,2,3 has established that almost all of the secondary electrons (SEs) produced by ionizing radiation can be lethal to the genome. 4 As a result, the new concepts that were developed during the studies of the mechanisms of action of LEEs 1,5 are starting to be applied to the development of new anti-cancer drugs 6,7,8 and the modification of clinical protocols. 9,10,11,12 Whereas the mechanisms of the direct action of LEEs on biomolecules are now fairly well understood, 4,5 the indirect effect of these electrons in irradiated cells remains unknown, owing essentially to the experimental difficulties associated with the production and observation of LEEs in aqueous media. Direct-type damage results from radiation energy being deposited directly into the DNA, whereas indirect damage occurs when the species created by the interaction of the primary radiation and SEs within the molecular environment surrounding the DNA (e.g., salts, proteins, oxygen and water) react with the molecule. 13,14 SEs with energies below 30 eV (i.e., LEEs) can attach to DNA components and thus form transient negative ions (TNIs) of DNA subunits (a base, sugar or phosphate group). In this manner, LEEs induce direct damage to DNA, such as single and double strand breaks (SSBs and DSBs) principally via the decay of TNIs into dissociating electronically excited states and dissociative electron attachment (DEA). 4,15 Since cells contain 70-80% water, 16 LEEs also react with water molecules near DNA in the cell nucleus and create reactive species to produce indirect damage.To estimate the relative contribution of the indirect and direct modes of damage of LEEs in cells, experiments were undertaken with thin films of short single DNA strands (i.e., oligonucleotides) embedded into biomolecular enviro...

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Dissociative electron attachment in nanoscale ice films: Thickness and charge trapping effects

Cited by 80 publications

References 48 publications

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

Absolute cross section for low-energy-electron damage to condensed macromolecules: A case study of DNA

Ion-induced electrostatic charging of ice at 15–160 K

Radiation Damage to DNA: The Indirect Effect of Low-Energy Electrons

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