Site-selective soft X-ray absorption as a tool to study protonation and electronic structure of gas-phase DNA

Abstract

The conformation and the electronic structure of gas-phase oligonucleotides depends strongly on the protonation site. 5’-d(FUAG) can either be protonated at the A-N1 or at the G-N7 position. We have...

Multiple valence electron detachment following Auger decay of inner-shell vacancies in gas-phase DNA

“…2d have been obtained. In qualitative agreement with our results for smaller, protonated oligonucleotides, 26 the spectra feature a strong increase between 285 eV and 292 eV that is due to resonant C 1s excitation into unoccupied molecular orbitals, mostly of π* character (see Fig. 2e , left).…”

“…This fact is even more clear, when zooming in on the small positive fragments (see Fig. 2c ): the most intense fragment GH + (152 Da) is due to glycosidic bond cleavage accompanied by double H/proton transfer, a very common process also observed in photofragmentation 26 but also in collision-induced dissociation 27 of protonated oligonucleotides. The peak at 135 Da is most likely formed by NH 3 loss from GH + , which is a common fragmentation channel in protonated guanine.…”

Intramolecular hydrogen transfer in DNA induced by site-selective resonant core excitation

“…The final states of the transitions contributing to both bands a N and b N all have π * character and are localized on the nucleobases. This is discussed in detail in ref [12].…”

“…The imine A-N1 atom of adenine is the most likely protonation site in [d( F UAG)+H] + . When A-N1 is protonated, the lowest energy absorption transition localized at A contributes to the b N band rather than to the a N band [12]. Band b N is generally comprising transitions on amine nitrogen atoms in all three nucleobases.…”

“…Resonant soft Xray absorption is therefore sensitive to the local electronic structure. In a recent study, we have utilized soft X-ray spectroscopy at the N K-edge to investigate the influence of the protonation site on the electronic structure of protonated [d F UAG+H] + at the nitrogen K-edge [12].…”