title: Primary fragmentation pathways of gas phase [M(uracil-H)(uracil)]+ complexes (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd , Mg, Ca, Sr, Ba, and Pb): loss of uracil versus HNCO.
abstract: Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive-ion electrospray spectra show that [M(Ura-H)(Ura)](+)  (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI-CID experiments show that the main primary decomposition pathway for all [M(Ura-H)(Ura)](+) , except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI-CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura-H)(Ura)](+)  are shown to lose a molecule of uracil. Similar results were observed under infrared multiple-photon dissociation excitation conditions, except that [Ca(Ura-H)(Ura)](+)  was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura-H)](+)  (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic-structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura-H)](+)  is ion-dipole complexation and the experimental evidence presented supports this.
authors.affiliation: Memorial University of Newfoundland, St. John's, NL, Canada.
authors.forename: Osama Y
authors.initials: OY
authors.lastname: Ali
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Randell
authors.forename: Travis D
authors.initials: TD
authors.lastname: Fridgen
mesh_terms: D003198:Computer Simulation; D056831:Coordination Complexes / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D015394:Molecular Structure; D044367:Phase Transition; D013816:Thermodynamics; D014498:Uracil / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D005740:Gases; D019216:Metals, Heavy; D014498:Uracil