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Updated: Apr 4, 2026

An Integrated Approach for Microprotein Identification and Sequence Analysis
Published on: July 12, 2022
Mode-specific fragmentation of amino acid-containing clusters
W Scott Hopkins1, Rick A Marta1, Vincent Steinmetz2
1Department of Chemistry, University of Waterloo, Waterloo, ON, CanadaN2L 3G1. shopkins@uwaterloo.ca mcmahon@uwaterloo.ca.
Abstract:
A combination of infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory calculations have been employed to study the structures and mode-specific dissociation pathways of the proton-bound dimer of 3-trifluoromethylphenylalanine (3-CF3-Phe) and trimethylamine (TMA). Three structural motifs are identified: canonical (charge-solvated), zwitterionic (charge-separated), and TMA-bridged. In the 1000-1350 cm(-1) region, similar spectra are observed in the TMA·H(+) and 3-CF3-Phe·H(+) product channels. At wavenumbers above 1350 cm(-1), infrared excitation of charge-solvated structures leads exclusively to production of protonated TMA, while excitation of zwitterionic or TMA-bridged structures results exclusively in production of protonated 3-CF3-Phe. The cluster potential energy landscape is topologically mapped and mechanisms for isomerization and mode-selective dissociation are proposed. In particular, cluster transparency as a result of IR-induced isomerization is implicated in deactivation of some IRMPD channels.
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