State-Dependent Fragmentation of Protonated Uracil and Uridine

Abstract

Tandem mass spectroscopy (MS 2 ) combined with single photon excitation in the VUV range (photon energy 4.5 − 9 eV) was performed on protonated uracil (UraH + ) and uridine (UrdH + ). The precursor ions with m/z 113 and m/z 245 respectively were produced by an Electrospray Ionization source (ESI) and accumulated inside a 1 arXiv:1902.02042v1 [physics.chem-ph] 6 Feb 2019 quadrupole ion trap mass spectrometer. After irradiation with tunable synchrotron radiation, product ion mass spectra were obtained. Fragment yields as a function of exciting energy show several maxima that can be attributed to the photo-excitation into different electronic states. For uracil, vertically excited states were calculated using the equation-of-motion coupled cluster approach (EOM-CCSD) and compared to the observed maxima. This allows to establish correlations between electronic states and resulting fragment masses and can thus help to disentangle the complex deexcitation and fragmentation pathways of nucleic acid building blocks above the first electronically excited state. Photofragmentation of the nucleoside uridine shows a significantly lower variety of fragments, indicating stabilization of the nucleobase by the attached sugar.

Excited state dynamics of protonated keto uracil: intersystem crossing pathways in competition

“…Besides, this state-dependent fragmentation pattern also depends on the probe wavelength. This strongly suggests that different electronic excited states can be reached by absorption of the probe photon leading to specific photofragments, as recently pointed out by Pitzer et al [51]. They established correlations between electronic states and photofragments observed through VUV photon excitation of room temperature UH + .…”

Thermal desorption effects on fragment ion production from multi-photon ionized uridine and selected analogues

“…nucleobases, then nucleosides, nucleotides, oligonucleotides, RNA/DNA strands and beyond. [10][11][12] Electrospray ionization sources can give access to experimentally-viable gas-phase targets across a great range of complexities, [13][14][15][16] but even the rst step in this sequence presents a challenge for neutrals due to thermal lability. 17,18 Accordingly, the experimental literature on neutral gas-phase nucleosides is sparse compared with nucleobases.…”

Electron-induced ionization and cationic fragmentations of the isolated molecule of 2,4-imidazolidinedione (hydantoin): a study of the relaxing path thresholds

“…These excited states evolve and after complex molecular mechanism(s), fragmentation takes place. Pitzer et al , 27 in the one-photon protonated uracil interaction in the 4.5–9.5 eV range, show that the yield of a given mass shows maxima that can be correlated to excited states.…”