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

Scheer, Adam M.; Aflatooni, Kayvan; Gallup, Gordon A; Burrow, Paul

doi:10.1103/physrevlett.92.068102

Cited by 209 publications

(254 citation statements)

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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%

“…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.…”

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confidence: 99%

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

2013

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“…13, 16, and 23-27͒ and the important role that vibrational Feshbach resonances associated with dipole-bound anion states appear to play in driving such dissociation. 15,23,27 No gas-phase total or elastic scattering cross section measurements for the nucleobases have, to our knowledge, been reported, except for the relative 90°differential cross sections for uracil and halouracils obtained by Abouaf and Dunet. 21 However, Scheer et al 15 and Aflatooni et al 39 have conducted valuable studies of the electron-transmission spectra for the nucleobases that reveal the energies of resonances in the lowenergy total scattering cross section, and they have assigned the features they see to * shape resonances.…”

Section: Introductionmentioning

confidence: 99%

Interaction of low-energy electrons with the purine bases, nucleosides, and nucleotides of DNA

Winstead¹,

McKoy²

2006

The Journal of Chemical Physics

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The authors report results from computational studies of the interaction of low-energy electrons with the purine bases of DNA, adenine and guanine, as well as with the associated nucleosides, deoxyadenosine and deoxyguanosine, and the nucleotide deoxyadenosine monophosphate. Their calculations focus on the characterization of the * shape resonances associated with the bases and also provide general information on the scattering of slow electrons by these targets. Results are obtained for adenine and guanine both with and without inclusion of polarization effects, and the resonance energy shifts observed due to polarization are used to predict * resonance energies in associated nucleosides and nucleotides, for which static-exchange calculations were carried out. They observe slight shifts between the resonance energies in the isolated bases and those in the nucleosides.

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“…They attributed the resonances to the vibrational levels of the dipole-bound anion. More recently, dipole-bound states have been attributed to a series of sharp peaks in the dissociative electron attachment cross sections of DNA bases, RNA base uracil, and the halouracils [19][20][21][22]. Similarly, here it will be shown that a dipole-bound state offers a more plausible explanation for the threshold peaks seen in the photoelectron energy distribution of HOCO − than electron scattering shape resonances.…”

Section: Introductionmentioning

confidence: 82%

Vibrational Feshbach resonances in near-threshold HOCO−photodetachment: A theoretical study

Miyabe

Haxton²,

Lawler³

et al. 2011

Phys. Rev. A

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The results of a theoretical study of HOCO − photodetachment are presented, with a view toward understanding the origin of two peaks observed by Lu and Continetti (Phys. Rev. Lett. 99, 113005 (2007)) in the photoelectron kinetic energy spectrum very close to threshold. It is shown that the peaks can be attributed to vibrational Feshbach resonances of dipole-bound trans-HOCO − , and not s-and p-wave shape resonances as previously assumed. Fixed-nuclei variational electron-HOCO scattering calculations are used to compute photodetachment cross sections and laboratory-frame photoelectron angular distributions. The calculations show a broad A ′′ (π*)-shape resonance several eV above threshold.

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

Cited by 209 publications

References 17 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

Interaction of low-energy electrons with the purine bases, nucleosides, and nucleotides of DNA

Vibrational Feshbach resonances in near-threshold HOCO−photodetachment: A theoretical study

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