Electronic Structure of Adenine and Thymine Base Pairs Studied by Femtosecond Electron−Ion Coincidence Spectroscopy

Gador, Niklas; Samoylova, Elena; Smith, Valoris Reid; Stolow, Albert; Rayner, D. M.; Radloff, W.; Hertel, I. V.; Schultz, Thomas

doi:10.1021/jp076800e

Cited by 36 publications

(62 citation statements)

References 57 publications

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“…While this does not discount the possible presence of clusters in the neutral beams [21], comparisons with previous experiments on adenine suggest that the supersonic expansion conditions were not suitable for significant cluster formation [22]. The ratio of 4 ± 3% for 136/135 Th counts in the adenine MPI data is broadly consistent with the ratio of 7.4% expected due to isotopomers [23]. By contrast, Kim et al's [24] MPI experiments (ns-timescale pulses at 266 nm) showed a major increase in the 136/135 Th ratio due to intermolecular proton transfer in adenine clusters (discussed further in Section 3.2).…”

Section: Resultssupporting

confidence: 64%

“…The measurements were carried out at relatively low laser fluence (average 4 × 10 5 W cm −2 , 225 nm) in an effort to reduce cluster dissociation via higher order (≥3) photon absorption. The measurement in dry conditions showed a very weak peak for A 2 + (0.2% of the A + signal) and the 136/135 Th ratio was 8.0 ± 0.4%, close to the expected isotopomer ratio of 7.4% [23]. This indicates that the adenine molecules were predominantly isolated.…”

Section: Resultssupporting

confidence: 58%

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Multi-photon and electron impact ionisation studies of reactivity in adenine–water clusters

Barc¹,

Ryszka²,

Poully³

et al. 2014

International Journal of Mass Spectrometry

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Keywords:Adenine Cluster Dissociative ionisation Hypoxanthine Multi-photon ionisation Electron impact ionisation a b s t r a c t Multi-photon ionisation (MPI) and electron impact ionisation (EII) mass spectrometry experiments have been carried out to probe unimolecular and intermolecular reactivities in hydrated adenine clusters. The effects of clustering with water on fragment ion production from adenine have been studied for the first time. While the observation of NH 4 + fragments indicated the dissociation of protonated adenine, the dominant hydration effects were enhanced C 4 H 4 N 4 + production and the suppression of dissociative ionisation pathways with high activation energies. These observations can be attributed to energy removal from the excited adenine radical cation via cluster dissociation. Comparisons of MPI and EII measurements provided the first experimental evidence supporting hypoxanthine formation in adenine-water clusters via theoretically predicted barrierless deamination reactions in closed shell complexes.

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Section: Resultssupporting

confidence: 64%

Section: Resultssupporting

confidence: 58%

Multi-photon and electron impact ionisation studies of reactivity in adenine–water clusters

Barc¹,

Ryszka²,

Poully³

et al. 2014

International Journal of Mass Spectrometry

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“…1 are in good agreement with the calculated spectra of glycine using particle-particle Green's function techniques [39]. Because of the large energy gap of about 15 eV between states dominated by ½ðO2sÞ −2 and ½ðN2sÞ −2 configurations, the electronic and nuclear dynamics initiated from the localized double-hole states at either atomic site can, in principle, be probed with complete knowledge of the initial electronic state of the ion by coincident detection of the energy of the Auger electron [40][41][42][43].…”

supporting

confidence: 72%

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

Vendrell

Santra

2015

Phys. Rev. Lett.

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We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-BornOppenheimer effects may affect the apparent electron densities extracted from such measurements.

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“…Finally, MPI and electron impact ionization (EII) experiments were carried out on uracil-adenine clusters as a step towards better understanding the dissociative ionization pathways of uracil within RNA. Whereas several spectroscopic studies have been carried out on adenine-thymine complexes in supersonic beams [18,19,20], to our knowledge no previous experiments on isolated uracil-adenine clusters have been reported in the literature. Ryszka et al Int.…”

Section: Introductionmentioning

confidence: 98%

Dissociative multi-photon ionization of isolated uracil and uracil-adenine complexes

Ryszka

Pandey

Rizk

et al. 2016

International Journal of Mass Spectrometry

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Recent multi-photon ionization (MPI) experiments on uracil revealed a fragment ion at m/z 84 that was proposed as a potential marker for ring opening in the electronically excited neutral molecule. The present MPI measurements on deuterated uracil identify the fragment as C 3 H 4 N 2 O + (uracil + less CO), a plausible dissociative ionization product from the theoretically predicted open-ring isomer. Equivalent measurements on thymine do not reveal an analogous CO loss channel, suggesting greater stability of the excited DNA base. MPI and electron impact ionization experiments have been carried out on uracil-adenine clusters in order to better understand the radiation response of uracil within RNA.Evidence for C 3 H 4 N 2 O + production from multi-photon-ionized uracil-adenine clusters is tentatively attributed to a significant population of π-stacked configurations in the neutral beam. Graphical AbstractHighlights UV multi-photon ionization measurements on deuterated uracil have identified a CO loss pathway that may indicate ring opening in the electronically excited neutral molecule. The first dissociative ionization experiments on uracil-adenine complexes have revealed that the CO loss channel is also accessible in these clusters.Keywords: Uracil; adenine-uracil clusters; fragmentation; multi-photon ionization; electron impact ionization; mass spectrometry Ryszka et al. Int. J. Mass. Spectrom. 396 (2016) 48 2 IntroductionThe dynamics and stabilities of nucleobases following excitation to their bright S 2 (ππ* of the ring-opening crossing seam [9] and the geometry of the predicted isomer indicates likely CO abstraction. Therefore MPI production of this fragment ion was proposed as a potential experimental marker for ring opening in neutral excited uracil, suggesting possibilities for diverse measurements exploring the process in depth (e.g. using coincidence and / or time-resolved methods). The first aim of the present work was to test if the new fragment ion is indeed due to CO loss by studying MPI of deuterated uracil (dominantly C 4 D 4 N 2 O 2 ). These results have the added value of identifying several previously debated fragments from the radical cation, while further evidence to assign specific peaks is provided by high-resolution MPI mass spectra. The paper also presents equivalent MPI measurements on thymine, for which no analogous ring-opening process has been predicted [9]. A distinctly higher pump energy (5.64 eV, 220 nm) was applied than in the previous MPI studies of thymine (4.34-4.77 eV, 285.7-260 nm) [6, 12, 13, 14, 15, 16, 17], increasing the likelihood of isomeric transitions during radiationless deactivation. Finally, MPI and electron impact ionization (EII) experiments were carried out on uracil-adenine clusters as a step towards better understanding the dissociative ionization pathways of uracil within RNA. Whereas several spectroscopic studies have been carried out on adenine-thymine complexes in supersonic beams [18,19,20], to our knowledge no previous experiments on isolated u...

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Electronic Structure of Adenine and Thymine Base Pairs Studied by Femtosecond Electron−Ion Coincidence Spectroscopy

Cited by 36 publications

References 57 publications

Multi-photon and electron impact ionisation studies of reactivity in adenine–water clusters

Multi-photon and electron impact ionisation studies of reactivity in adenine–water clusters

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

Dissociative multi-photon ionization of isolated uracil and uracil-adenine complexes

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