title: Direct evidence for tautomerization of the uracil moiety within the Pb2+/uridine-5'-monophosphate complex: a combined tandem mass spectrometry and IRMPD study.
abstract: The structure of the [Pb(UMP)-H](+) (UMP = uridine-5'-monophosphate) complex was studied in the gas phase by combining electrospray ionization (ESI), tandem mass spectrometry, and mid-infrared multiple photon dissociation (IRMPD) spectroscopy. The results obtained show that Pb(2+) ions interact not only with the deprotonated phosphate group but also with a carbonyl group of the nucleobase moiety by folding of the mononucleotide, resulting in macrochelates that are not likely to be present in solution. Comparison between the IRMPD and DFT-computed spectra suggests that the ESI-generated complex likely corresponds to a mixture of several structures, and establishes the enolic tautomers as the most abundant species for the [Pb(UMP)-H](+) ion, while the very weak IRMPD signal observed at ∼1763 cm(-1) points to a minor population of oxo forms. Our data also suggest that losing the nucleobase residue under CID conditions does not necessarily mean a lack of interaction between the metal and the nucleobase moiety, as commonly reported in the literature for large oligonucleotides.
authors: Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, Université d'Evry Val d'Essonn e, Bâtiment Maupertuis, Boulevard François Mitterrand, 91025 Evry, France. jean-yves.salpin@univ-evry.fr
authors: Jean-Yves
authors: JY
authors: Salpin
authors: Sébastien
authors: S
authors: Guillaumont
authors: Daniel
authors: D
authors: Ortiz
authors: Jeanine
authors: J
authors: Tortajada
authors: Philippe
authors: P
authors: Maître
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D005740:Gases; D007477:Ions; D007854:Lead / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D044367:Phase Transition; D012996:Solutions; D013055:Spectrophotometry, Infrared; D053719:Tandem Mass Spectrometry; D014498:Uracil / Q000737:chemistry*; D014542:Uridine Monophosphate / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D005740:Gases; D007477:Ions; D012996:Solutions; D007854:Lead; D014498:Uracil; D014542:Uridine Monophosphate