Selectivity in fragmentation of N-methylacetamide after resonant K-shell excitation

Phys Chem Chem Phys. 2014 Aug 7;16(29):15231-40. doi: 10.1039/c4cp01067a.

Abstract

The fragmentation pattern of the peptide model system, N-methylacetamide, is investigated using ion time-of-flight (TOF) spectroscopy after resonant K-shell excitation. Corresponding near-edge X-ray absorption fine structure (NEXAFS) spectra recorded at high resolution at the C1s, N1s and O1s edges are presented. Analysis of the ion TOF data reveals a multitude of fragmentation channels and dissociation pathways. Comparison between the excitation of six different resonances in the vicinity of the C1s, N1s and O1s edges suggests evidence for site-selective bond breaking. In particular the breaking of the peptide bond and the N-C(α) bond show a clear correlation with resonant excitation at the N1s edge. Also, stronger tendencies towards site-selective bond breaking are found for the generation of single ions compared with ion pairs. Analysis of angular distributions of ions from breakage of the peptide bond yields a fragmentation time of <400 fs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetamides / chemistry*
  • Ions
  • Models, Chemical
  • Peptide Fragments / chemistry*
  • X-Ray Absorption Spectroscopy*

Substances

  • Acetamides
  • Ions
  • Peptide Fragments
  • N-methylacetamide