Electron attachment to the dipeptide dialanine: influence of methylation on site selective dissociation reactions

Benjamin Puschnigg, Stefan E. Huber, Michael Probst, Katrin Tanzer, Violaine Vizcaino, Filipe Ferreira da Silva, Paul Scheier, Paulo Limao-Vieira, Stephan Denifl

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11 Citations (Scopus)

Abstract

Gas phase dissociative electron attachment (DEA) measurements with methyl-dialanine, C7H14N2O3, are performed in a crossed electron-molecular beam experiment at high energy resolution (similar to 120 meV). Anion efficiency yields as a function of the incident electron energy are obtained for the most abundant fragments up to electron energies of similar to 15 eV. There is no evidence of molecular anion formation whereas the dehydrogenated closed shell anion (M-H)(-) is one of the most dominant reaction products. Quantum chemical calculations are performed to investigate the electron attachment process and to elucidate site selective bond cleavage in the (M-H)(-) DEA-channel. Previous DEA studies on dialanine have shown that (M-H)(-) formation proceeds through abstraction of a hydrogen atom from the carboxyl and amide groups, contributing to two distinct resonances at 0.81 and 1.17 eV, respectively [D. Gschliesser, V. Vizcaino, M. Probst, P. Scheier and S. Denifl, Chem.-Eur. J., 2012, 18, 4613-4619]. Here we show that by methylation of the carboxyl group, all (calculated) thresholds for H-loss from the different sites in the dialanine molecule are shifted up to a maximum of 1.4 eV. The lowest lying resonance observed experimentally for (M-H)(-) remains operative from the amide group at the electron energy of 2.4 eV due to the methylation. We further study methylation-induced effects on the unimolecular dissociation leading to a variety of negatively charged DEA products.
Original languageEnglish
Pages (from-to)3834-3840
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume15
Issue number11
DOIs
Publication statusPublished - 21 Mar 2013

Keywords

  • LOW-ENERGY ELECTRONS
  • GAS-PHASE GLYCINE
  • MOLECULAR-ORBITAL METHODS
  • GAUSSIAN-BASIS SETS
  • DNA STRAND BREAKS
  • AMINO-ACIDS
  • ATOMS
  • CAPTURE
  • ANION
  • FRAGMENTATION

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