Study of Electron Ionization and Fragmentation of Non-hydrated and Hydrated Tetrahydrofuran Clusters

Abstract

Mass spectroscopic investigations on tetrahydrofuran (THF, C4H8O), a common model molecule of the DNA-backbone, have been carried out. We irradiated isolated THF and (hydrated) THF clusters with low energy electrons (electron energy ~70 eV) in order to study electron ionization and ionic fragmentation. For elucidation of fragmentation pathways, deuterated TDF (C4D8O) was investigated as well. One major observation is that the cluster environment shows overall a protective behavior on THF. However, also new fragmentation channels open in the cluster. In this context, we were able to solve a discrepancy in the literature about the fragment ion peak at mass 55 u in the electron ionization mass spectrum of THF. We ascribe this ion yield to the fragmentation of ionized THF clusters. Graphical Abstractᅟ

High‐energy collision‐induced dissociation of histidine ions [His + H]+ and [His − H]− and histidine dimer [His2 + H]+

“…These two product ions highlight cleavages in one of the His molecules, while the hydrogen bond between the monomers is maintained. We note that such preference of intramolecular bond cleavage over intermolecular bond cleavage was recently observed in a variety of non‐covalently bound clusters . The preference of His to undergo protonation at the imidazole ring, and the observation of both of these product ions, suggest that the His dimer [His 2 + H] + is bound through a shared proton between the imidazole moieties.…”

“…We note that such preference of intramolecular bond cleavage over intermolecular bond cleavage was recently observed in a variety of non-covalently bound clusters. [38][39][40] The preference of His to undergo protonation at the imidazole ring, 4,6 and the observation of both of these product ions, suggest that the His dimer [His 2 + H] + is bound through a shared proton between the imidazole moieties. However, further theoretical investigations would be desirable to prove our suggestion.…”

Water acting as a catalyst for electron-driven molecular break-up of tetrahydrofuran

“…Consequently, a number of studies on pure and nano-hydrated biomolecular clusters have been performed using different mass spectrometric techniques for both cations and anions [7][8][9][10][11][12][13][14][15][16] . The effect of solvation on the fragmentation of biomolecules after collisions with various projectiles was studied by measuring the yields of different fragment ions.…”

Electron ionization of clusters containing the formamide molecule

“…The clusters are formed by supersonic expansion in a versatile cluster source consisting of a nozzle, connecting lines to a sample container and a flow controller to introduce argon as seeding gas (see [ 37 ] for a typical configuration of the cluster source). The sample containers are located outside the vacuum chamber in order to refill the container without breaking the high-vacuum after the nozzle.…”

“…Since the ion source chamber pressure corresponds to that of single collision conditions, FAH + is formed by the break-up of an ionized formamide cluster, most probably from the ionized dimer. The observation of protonated parent (cluster) ions is characteristic for hydrogen-containing molecules and a highly abundant species upon electron ionization of clusters [37,[40][41][42][43][44][45]. The structures and energies of the neutral formamide dimer were the focus of few theoretical and experimental studies previously.…”