Hydration structures of 2′-deoxyguanosine studied by IR-UV double resonance spectroscopy: comparison with guanosine

Abstract

Infrared spectra of mono- and dihydrated clusters of 2'-deoxyguanosine (2'-dGs), which are formed by laser desorption combined with supersonic jet-cooling, have been measured by the technique of IR-UV double resonance spectroscopy. The structures of these hydrates are compared with those reported for guanosine (Gs) to elucidate the importance of the 2'-hydroxy group in the hydration. It is shown that monohydrated structures observed for 2'-dGs are similar to those of Gs, indicating no significant influence by the absence of 2'-OH group. For the dihydrated cluster, two structural isomers are identified and assigned to the dihydrates with the guanine moiety is in the keto form, which are consistent with the lowest-energy structures derived from theoretical calculations. Comparison with the results for Gs suggests that the presence of 2'-OH group leads to the stabilization of specific dihydrate structures involving the sugar group.

How nature covers its bases

“…By controlling the source conditions, it is also possible to generate clusters of desorbed molecules with each other or with water molecules to mimic base pairs and microsolvation. [65][66][67][68][69][70][71][72] Downstream, the jet cooled molecules are excited and photo-ionized and the ions are detected in a time-of-flight mass spectrometer. 64,[73][74] Figure 2 shows a schematic overview of the most common laser spectroscopy approaches to studying neutral molecules in the gas phase.…”

Structural identification of uric acid and its monohydrates by IR-UV double resonance spectroscopy

“…In our previous studies, 2,3 we have investigated hydrated clusters of guanosine and 2 0 -deoxyguanosine and found that the presence of the sugar group leads to the stabilization of specific hydration structures. Furthermore, the keto-enol tautomerization and excited-state dynamics of these nucleosides are significantly influenced by the hydration.…”

Gas-phase formation and reactions of radical cations of guanosine, deoxyguanosine and their homodimers and heterodimers

“…Thus dG •+ and Gs •+ , formed either in the source or from the [Cu II dG 3 ] 2+ and [Cu II Gs 3 ] 2+ precursor complexes, have different structures to those formed from the dimer radical cations. Although this appears to be a novel finding in terms of tautomerisation within gas-phase supramolecular complexes, a search of the literature reveals examples of different gas-phase tautomeric forms of neutral dG and Gs that arise from the way that they are generated in the gas-phase [40][41][42]. Thus IR spectroscopy with resonant two-photon ionisation has been used to show that neutral dG and Gs formed via laser desorption exist in the enol forms D1 and D2 [40], but when hydrated by one or two water molecules, exist in the keto forms C1 and C2 [41,42].…”

“…Although this appears to be a novel finding in terms of tautomerisation within gas-phase supramolecular complexes, a search of the literature reveals examples of different gas-phase tautomeric forms of neutral dG and Gs that arise from the way that they are generated in the gas-phase [40][41][42]. Thus IR spectroscopy with resonant two-photon ionisation has been used to show that neutral dG and Gs formed via laser desorption exist in the enol forms D1 and D2 [40], but when hydrated by one or two water molecules, exist in the keto forms C1 and C2 [41,42]. It is also worth mentioning that CID of metal complexes of amino acids and peptides can give rises to isomeric radical cations that depend on the metal complex [43][44][45].…”