NCO/sup>, a Key Fragment Upon Dissociative Electron Attachment and Electron Transfer to Pyrimidine Bases: Site Selectivity for a Slow Decay Process

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• 作者：Filipe Ferreira da Silva (1)
  Carolina Matias (1) (2)
  Diogo Almeida (1)
  Gustavo Garc (3)
  Oddur Ingfsson (4)
  Helga Dgg Flosadtir (4)
  Benedikt arsson (4)
  Sylwia Ptasinska (5)
  Benjamin Puschnigg (2)
  Paul Scheier (2)
  Paulo Limo-Vieira (1)
  Stephan Denifl (2)
  
• 关键词：NCO anion ; Electron transfer ; Negative ion formation ; Metastable decay ; DEA ; Collision dynamics ; Matrix assisted laser desorption/ionization (MALDI)
• 刊名：Journal of The American Society for Mass Spectrometry
• 出版年：2013
• 出版时间：November 2013
• 年：2013
• 卷：24
• 期：11
• 页码：1787-1797
• 全文大小：
• 作者单位：Filipe Ferreira da Silva (1)
  Carolina Matias (1) (2)
  Diogo Almeida (1)
  Gustavo Garc (3)
  Oddur Ingfsson (4)
  Helga Dgg Flosadtir (4)
  Benedikt arsson (4)
  Sylwia Ptasinska (5)
  Benjamin Puschnigg (2)
  Paul Scheier (2)
  Paulo Limo-Vieira (1)
  Stephan Denifl (2)
  
  1. Laboratio de Colises Aticas e Moleculares, CEFITEC, Departamento de Fica, Faculdade de Cicias e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516, Caparica, Portugal
  2. Institut f Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck, Leopold-Franzens Universitt Innsbruck, Technikerstr. 25, 6020, Innsbruck, Austria
  3. Instituto de Fica Fundamental, Consejo Superior de Investigaciones Cienticas (CSIC), Serrano 113-bis, 28006, Madrid, Spain
  4. Department of Chemistry and Science Institute, University of Iceland, Dunhagi 3, 107, Reykjavik, Iceland
  5. Department of Physics and Radiation Laboratory, University of Notre Dame, Notre Dame, IN, 46556, USA
  
• ISSN：1879-1123

文摘

We report gas phase studies on NCO/sup> fragment formation from the nucleobases thymine and uracil and their N-site methylated derivatives upon dissociative electron attachment (DEA) and through electron transfer in potassium collisions. For comparison, the NCO/sup> production in metastable decay of the nucleobases after deprotonation in matrix assisted laser desorption/ionization (MALDI) is also reported. We show that the delayed fragmentation of the dehydrogenated closed-shell anion into NCO/sup> upon DEA proceeds few microseconds after the electron attachment process, indicating a rather slow unimolecular decomposition. Utilizing partially methylated thymine, we demonstrate that the remarkable site selectivity of the initial hydrogen loss as a function of the electron energy is preserved in the prompt as well as the metastable NCO/sup> formation in DEA. Site selectivity in the NCO/sup> yield is also pronounced after deprotonation in MALDI, though distinctly different from that observed in DEA. This is discussed in terms of the different electronic states subjected to metastable decay in these experiments. In potassium collisions with 1- and 3-methylthymine and 1- and 3-methyluracil, the dominant fragment is the NCO/sup> ion and the branching ratios as a function of the collision energy show evidence of extraordinary site-selectivity in the reactions yielding its formation. Graphical abstract