Photofragmentation in selected tautomers of protonated adenine

Cheong, Nu Ri; Nam, Sang Hwan; Park, Hye Sun; Ryu, Soojung; Song, Jae Kyu; Park, Seung Min; Pérot, Marie; Lucas, Bruno; Barat, M.; Fayeton, J. A.; Jouvet, Christophe

doi:10.1039/c000961j

Cited by 31 publications

(42 citation statements)

References 27 publications

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“…In this ion Fig 5a). No peak at m/z 84 has been observed from isolated, clustered, or protonated adenine [22,37,39,40], or from protonated uracil [41]. The fact that the U + signals were the same (to within the uncertainty limits) in plots a and c as well as in plots b and d suggests that this result was not simply due to different populations of isolated uracil molecules in the neutral beams.…”

Section: Fig 5 Compares Mpi and Eii Measurements Carried Out On Uracsupporting

confidence: 52%

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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Section: Fig 5 Compares Mpi and Eii Measurements Carried Out On Uracsupporting

confidence: 52%

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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“…The 3H-9H tautomer can probably be ruled out since its absorption lies in the 320 nm region 13 and, taking into account the ion trap temperature and the ground state energies, the population of this species is expected to be very low. In the low energy system the intensity of the m/z=94 and m/z=119 fragments arising from H 2 NCN and NH 3 loss are the same whereas on the higher energy band system the m/z 119 fragment becomes more intense than m/z 94.…”

Section: E-adenineh +mentioning

confidence: 99%

“…22 Due to numerous conical intersections between the n and * states, the excited state optimization is not straightforward and failed in many systems as shown already for protonated adenine. 12,13 Calculations were performed with the correlation-consistent polarized valence double-zeta (cc-pVDZ or aug-cc-pVDZ) basis set. 23 The vibrations in the ground and excited states have been calculated for the enol/1H-2H 24 tautomer of protonated cytosine and the electronic spectra simulated using the Pgopher software 25 for Franck Condon analysis.…”

Section: B Calculationsmentioning

confidence: 99%

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Excited states of protonated DNA/RNA bases

Berdakin

Féraud

Dedonder‐Lardeux

et al. 2014

Phys. Chem. Chem. Phys.

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155

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The very fast relaxation of the excited states to the ground state in DNA/RNA bases is a necessary process to ensure the photostability of DNA and its rate is highly sensitive to the tautomeric form of the bases.Protonation of the bases plays a crucial role in many biochemical and mutagenic processes and it can result in alternative tautomeric structures, thus making important the knowledge of the properties of protonated DNA/RNA bases. We report here the photofragmentation spectra of the five protonated DNA/RNA bases. In most of the cases, the spectra exhibit well resolved vibrational structures, with broad bands associated with very short excited state lifetimes. The similarity between the electronic properties e.g. excitation energy and very short excited state lifetimes for the canonical tautomers of protonated and neutral DNA bases, suggests that the former could also play an important role in the photostability mechanism of DNA.2

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“…The only previous studies of adenine dissociative ionisation in clusters were carried out on pure adenine complexes using MPI (266 nm ns-timescale laser pulses) [38] [38] MPI experiments on adenine clusters (minor peaks were mentioned but not listed); both strong photodissociation products of protonated adenine. The present work provides the first data on how clustering with water affects fragment ion production from adenine.…”

Section: Hydration Effects On Fragment Ion Production From Adeninementioning

confidence: 99%

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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Photofragmentation in selected tautomers of protonated adenine

Cited by 31 publications

References 27 publications

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

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

Excited states of protonated DNA/RNA bases

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

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