title: Tautomerism of uracil probed via infrared spectroscopy of singly hydrated protonated uracil.
abstract: Tautomerism of the nucleobase uracil is characterized in the gas phase through IR photodissociation spectroscopy of singly hydrated protonated uracil created with tandem mass spectrometric methods in a commercially available Fourier transform ion cyclotron resonance mass spectrometer. Protonated uracil ions generated by electrospray ionization are re-solvated in a low-pressure collision cell filled with a mixture of water vapor seeded in argon. Their structure is investigated by IR photodissociation spectroscopy in the NH and OH stretching region (2500-3800 cm(-1)) with a tabletop IR laser source and in the 1000-2000 cm(-1) range with a free-electron laser. In both regions the IR photodissociation spectrum exhibits well-resolved spectral signatures that point to the presence of two different types of structure for monohydrated protonated uracil, which result from the two lowest-energy tautomers of uracil. Ab initio calculations confirm that no water-catalyzed tautomerization occurs during the re-solvation process, indicating that the two protonated forms of uracil directly originate from the electrospray process.
authors.affiliation: FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439 MN Nieuwegein, The Netherlands.
authors.forename: Joost M
authors.initials: JM
authors.lastname: Bakker
authors.forename: Rajeev K
authors.initials: RK
authors.lastname: Sinha
authors.forename: Thierry
authors.initials: T
authors.lastname: Besson
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brugnara
authors.forename: Paolo
authors.initials: P
authors.lastname: Tosi
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Salpin
authors.forename: Philippe
authors.initials: P
authors.lastname: Maître
mesh_terms: D000042:Absorption; D007536:Isomerism; D007659:Ketones / Q000737:chemistry; D013058:Mass Spectrometry; D010782:Photolysis; D011522:Protons; D013055:Spectrophotometry, Infrared; D014498:Uracil / Q000737:chemistry*
chemical_list: D007659:Ketones; D011522:Protons; D014498:Uracil