Inelastic interactions of protons and electrons with biologically relevant molecules

Coupier, B.; Farizon, B.; Farizon, M.; Gaillard, M.J.; Gobet, F.; Faria, N. V. de Castro; Jalbert, Ginette; Ouaskit, S.; Carré, Michel; Gstir, B.; Hanel, G.; Denifl, Stephan; Feketeová, Linda; Scheier, P.; Märk, T.D.

doi:10.1140/epjd/e2002-00166-3

Cited by 96 publications

(65 citation statements)

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“…This fragment ion is not formed by direct excitation of gasphase uracil to ionic states, for example in single collisions with electrons or ions [27]. Aside from MPI with a pump wavelength ≤232 nm [11], m/z 84 ions from uracil have only been observed in laserinduced plasmas (266 and 1064 nm ns-timescale pulses) [28] where multiple collisions can plausibly lead to the ionization of excited neutral isomers.…”

Section: Methodsmentioning

confidence: 99%

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: Methodsmentioning

confidence: 99%

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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“…Table I lists the peaks observed at 220 nm. Dissociative ionization of uracil has been studied extensively by electron impact, [23][24][25][26][27][28] ion impact, [28][29][30][31][32][33][34][35] and single photon absorption. 21 Taking into account differences in energy deposition and signal/noise ratios, the previous experiments were broadly consistent in terms of the fragment ions produced and three high-resolution examples are summarized in Table I.…”

Section: A Non-dissociative Mpi Of Isolated Uracilmentioning

confidence: 99%

Multi-photon ionization and fragmentation of uracil: Neutral excited-state ring opening and hydration effects

Barc

Ryszka

Spurrell

et al. 2013

The Journal of Chemical Physics

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Multi-photon ionization (MPI) of the RNA base uracil has been studied in the wavelength range 220–270 nm, coinciding with excitation to the S2(ππ*) state. A fragment ion at m/z = 84 was produced by 2-photon absorption at wavelengths ≤232 nm and assigned to C3H4N2O+ following CO abstraction. This ion has not been observed in alternative dissociative ionization processes (notably electron impact) and its threshold is close to recent calculations of the minimum activation energy for a ring opening conical intersection to a σ(n-π)π* closed shell state. Moreover, the predicted ring opening transition leaves a CO group at one end of the isomer, apparently vulnerable to abstraction. An MPI mass spectrum of uracil-water clusters is presented for the first time and compared with an equivalent dry measurement. Hydration enhances certain fragment ion pathways (particularly C3H3NO+) but represses C3H4N2O+ production. This indicates that hydrogen bonding to water stabilizes uracil with respect to neutral excited-state ring opening.

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“…With the increasing use of proton and carbon ions in cancer treatment, interaction of ions with molecules from biological tissue was shifted into focus [1][2][3][4][5]. In these radiotherapy modalities, treatment planning is not only based on the conventional dosimetric quantity, namely, the absorbed dose to water.…”

Section: Introductionmentioning

confidence: 99%

Ion induced fragmentation cross-sections of DNA constituents

et al. 2015

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Abstract. Proton collision with chemical analogs for the base, the sugar and the phosphor residue of the DNA, namely pyrimidine, tetrahydrofuran and trimethyl phosphate, respectively, has been investigated. The impact energies ranged from 300 keV up to 16 MeV. For the first time, relative fragmentation crosssections for proton impact are reported for tetrahydrofuran and trimethyl phosphate; previously reported cross sections for pyrimidine are extended for energies beyond 2500 keV. Ionization of tetrahydrofuran leads to a ring break in about 80% of all events, trimethyl phosphate predominantly fragments by bond cleavage to one of the three methyl-groups and for pyrimidine the parent ion has the highest abundance. Such comparison supports earlier findings that the sugar is the weak spot for strand breaks.

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Inelastic interactions of protons and electrons with biologically relevant molecules

Cited by 96 publications

References 1 publication

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

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

Multi-photon ionization and fragmentation of uracil: Neutral excited-state ring opening and hydration effects

Ion induced fragmentation cross-sections of DNA constituents

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