title: N-site de-methylation in pyrimidine bases as studied by low energy electrons and ab initio calculations.
abstract: Electron transfer and dissociative electron attachment to 3-methyluracil (3meU) and 1-methylthymine (1meT) yielding anion formation have been investigated in atom-molecule collision and electron attachment experiments, respectively. The former has been studied in the collision energy range 14-100 eV whereas the latter in the 0-15 eV incident electron energy range. In the present studies, emphasis is given to the reaction channel resulting in the loss of the methyl group from the N-sites with the extra charge located on the pyrimidine ring. This particular reaction channel has neither been approached in the context of dissociative electron attachment nor in atom-molecule collisions yet. Quantum chemical calculations have been performed in order to provide some insight into the dissociation mechanism involved along the N-CH3 bond reaction coordinate. The calculations provide support to the threshold value derived from the electron transfer measurements, allowing for a better understanding of the role of the potassium cation as a stabilising agent in the collision complex. The present comparative study gives insight into the dynamics of the decaying transient anion and more precisely into the competition between dissociation and auto-detachment.
authors.affiliation: Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors.forename: D
authors.initials: D
authors.lastname: Almeida
authors.forename: D
authors.initials: D
authors.lastname: Kinzel
authors.forename: F
authors.initials: F
authors.lastname: Ferreira da Silva
authors.forename: B
authors.initials: B
authors.lastname: Puschnigg
authors.forename: D
authors.initials: D
authors.lastname: Gschliesser
authors.forename: P
authors.initials: P
authors.lastname: Scheier
authors.forename: S
authors.initials: S
authors.lastname: Denifl
authors.forename: G
authors.initials: G
authors.lastname: García
authors.forename: L
authors.initials: L
authors.lastname: González
authors.forename: P
authors.initials: P
authors.lastname: Limão-Vieira
mesh_terms: D004583:Electrons; D008745:Methylation; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D011743:Pyrimidines; C030986:pyrimidine