Electron Attachment to Uracil: Effective Destruction at Subexcitation Energies

Hanel, G.; Gstir, B.; Denifl, Stephan; Scheier, P.; Probst, Michael; Farizon, B.; Farizon, M.; Illenberger, Eugen; Td, Märk

doi:10.1103/physrevlett.90.188104

Cited by 324 publications

(340 citation statements)

References 33 publications

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“…6,7,12−14,37 Electron transmission spectroscopy and DEA studies have estimated the threshold energy for this channel to be at most 0.8 eV. 6,12 In our experiment, the analogous process could occur via…”

mentioning

confidence: 62%

Time-Resolved Radiation Chemistry: Photoelectron Imaging of Transient Negative Ions of Nucleobases

2013

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Time-resolved photoelectron imaging has been utilized to probe the energetics and dynamics of the transient negative ion of the nucleobase uracil. This species was created through charge transfer from an iodide anion within a binary iodide-uracil complex using a UV pump pulse; the ensuing dynamics were followed by photodetachment with a near-IR probe pulse. The photoelectron spectra show two time-dependent features, one from probe-induced photodetachment of the transient anion state and another from very low energy electron signal attributed to autodetachment. The transient anion was observed to decay biexponentially with time constants of hundreds of femtoseconds and tens of picoseconds, depending on the excitation energy. These dynamics are interpreted in terms of autodetachment from the initially excited state and a second, longer-lived species relaxed by iodine loss. Hydrogen loss from the N1 position may also occur in parallel.T he observation that low-energy electrons can lead to DNA and RNA strand cleavage via temporary negative ion states 1 has motivated numerous studies of nucleic acid constituents. Gas-phase studies of DNA and RNA building blocks, including individual nucleobases, nucleosides, and nucleotides, have sought to provide insight into the mechanisms of this radiation damage. 2 Transient anion states of nucleobases have been posited to play a major role in DNA mutagenesis, perhaps via a charge-transfer process from an initially charged nucleobase moiety to a sugar-phosphate bond. 3,4 In this work, we explore the dynamics of transient anion states of uracil via time-resolved photoelectron (TRPE) imaging 5 of an iodide-uracil binary complex.The interaction of excess electrons with uracil and other nucleobases has been studied in the gas phase using low-energy electron scattering, 6,7 negative ion photoelectron spectroscopy (PES), 8−10 and Rydberg electron transfer (RET). 11 Total electron scattering cross section measurements showed structure below 2 eV associated with unoccupied π* orbitals of uracil, 6 while dissociative electron attachment (DEA) studies showed that hydrogen atom loss from the N1 position in the transient negative ion U* − occurs at collision energies as low as 0.7 eV. 6,7,12−14 The nature of the uracil anion has been directly probed in PES and RET studies. PES experiments have measured the binding energy of the dipole-bound species as ∼90 meV 8,9 and estimate that valence anions of uracil bind excess electrons by tens to hundreds of meV. 9−11 These species are clearly distinguishable in photoelectron (PE) spectra, as dipolebound states consist of narrow features with low electron binding energies, reflecting the similarity between the anion and neutral geometries, while valence-bound anions have characteristically broader features. 15 Only dipole-bound anions of uracil have been observed using conventional ion generation methods, 8−10 but the uracil anion can transform from a dipolebound state to a valence-bound state upon complexation with one Xe atom or water...

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confidence: 62%

Time-Resolved Radiation Chemistry: Photoelectron Imaging of Transient Negative Ions of Nucleobases

2013

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“…Owing to resonance rearrangements in the electron system, the negative charge that might be expected to reside on N 1 after the H atom leaves is distributed widely over the molecule. This occurs more readily for this H atom than that on N 3 , and we attribute the low threshold for production of U-H ÿ H in uracil, reported by the calculations of Hanel et al [2] to be 0:8 0:1 eV, to this cause. In fact, the threshold may be as low as 0.6 eV, if these authors have ignored the change in zero point energy.…”

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confidence: 84%

“…This work, in part, has served to motivate further gas phase studies of electron collisions with the DNA bases, the RNA base uracil, and the halouracils in an effort to understand the fundamental mechanisms involved. Most recently, Hanel et al [2] (uracil), Denifl et al [3] (uracil, thymine and cytosine), Abouaf et al [4] (thymine and 5-bromouracil), and Denifl et al [5] (5-chlorouracil) have examined the electron energy dependence of the production of various anion fragments and made estimates of the magnitudes of the dissociative electron attachment (DEA) cross sections. The radiological significance of the halouracils has been discussed in several of these references and will not be repeated here.…”

mentioning

confidence: 99%

Bond Breaking and Temporary Anion States in Uracil and Halouracils: Implications for the DNA Bases

et al. 2004

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“…Gas phase experiments [43,46,47,48,49,50,51,52] revealed that below the electronic excitation energy level (3-4 eV), the TNI that are most likely to form are shape resonances of the basic subunits of DNA. At higher energies the TNI formed are Feshbach resonances.…”

Section: Dna Damage By Low-energy Electronsmentioning

confidence: 99%

Interactions between low energy electrons and DNA: a perspective from first-principles simulations

Kohanoff¹,

McAllister²,

Tribello³

et al. 2017

J. Phys.: Condens. Matter

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Abstract. DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts from the interaction of radiation -either photons or swift ions -with the biological medium. Such interactions cause electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals. Both of these species can cause damage to biological molecules, in particular DNA. In the long run, this molecular level damage can prevent cells from replicating and can hence lead to cell death. For a long time it was assumed that the main actors in the damage process were the radicals. However, experiments in a seminal paper by the group of Leon Sanche in 2000 showed that low-energy electrons (LEE), such as those generated when ionising biological targets, can also cause bond breaks in biomolecules, in particular strand breaks in plasmid DNA [1]. These results prompted a significant amount of experimental and theoretical work aimed at elucidating the role played by LEE in DNA damage.In this Topical Review we provide a general overview of the problem. We discuss experimental findings and theoretical results hand in hand with the aim of describing the physics and chemistry that occurs during the process of radiation damage, from the initial stages of electronic excitation, through the inelastic propagation of electrons in the medium, the interaction of electrons with DNA, and the chemical end-point effects on DNA. A very important aspect of this discussion is the consideration of a realistic, physiological environment. The role played by the aqueous solution and the amino acids from the histones in chromatin must be considered. Moreover, thermal fluctuations must be incorporated when studying these phenomena. Hence, a special place in this Topical Review is occupied by our recent first-principles molecular dynamics simulations that address the issue of how the environment favours or prevents LEEs from causing damage to DNA. We finish by summarising the conclusions achieved so far, and by suggesting a number of possible directions for further study.

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Electron Attachment to Uracil: Effective Destruction at Subexcitation Energies

Cited by 324 publications

References 33 publications

Time-Resolved Radiation Chemistry: Photoelectron Imaging of Transient Negative Ions of Nucleobases

Time-Resolved Radiation Chemistry: Photoelectron Imaging of Transient Negative Ions of Nucleobases

Bond Breaking and Temporary Anion States in Uracil and Halouracils: Implications for the DNA Bases

Interactions between low energy electrons and DNA: a perspective from first-principles simulations

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