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Title: Revealing the structure of isolated peptides: IR-IR predissociation spectroscopy of protonated triglycine isomers

Here, we report an isomer specific IR-IR double resonance study of the mass-selected protonated triglycine peptide. Comparison of experimental spectra with calculations reveals the presence of two isomers, with protonation occurring at either the terminal amine site or one of the amide oxygen sites. The amine protonated isomer identified in our experiment contains an atypical cis amide configuration as well as a more typical trans amide. The amide protonated peptide, on the other hand, contains two trans amide moieties. Both isomers are found to be the lowest energy structures for their respective protonation site, but it is unclear, from experiments and calculations, which one is the global minimum. The presence of both in our experiments likely points to kinetic trapping of a higher energy structure. Lastly, the observed frequencies of the NH and OH stretch vibrations are used to estimate the hydrogen-bond strengths present in each isomer, accounting for the relative stabilities of these structures.
 [1] ;  [1] ; ORCiD logo [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Molecular Spectroscopy
Additional Journal Information:
Journal Volume: 347; Journal Issue: C; Journal ID: ISSN 0022-2852
Research Org:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Infrared spectroscopy; Ions; Mass spectrometry; Peptide
OSTI Identifier: