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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.
Physical Chemistry Chemical Physics : PCCP
|September 9, 2015
Summary
Infrared spectroscopy and theory reveal distinct structures and dissociation pathways for proton-bound dimers of 3-trifluoromethylphenylalanine and trimethylamine. Mode-specific fragmentation depends on the initial cluster structure.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Spectroscopy
Background:
- Proton-bound dimers are crucial intermediates in various chemical processes.
- Understanding their structure-dissociation relationships is key to controlling chemical reactions.
Purpose of the Study:
- To investigate the structural motifs and dissociation mechanisms of the proton-bound dimer of 3-trifluoromethylphenylalanine (3-CF3-Phe) and trimethylamine (TMA).
- To explore mode-specific dissociation pathways influenced by infrared multiple photon dissociation (IRMPD) spectroscopy.
Main Methods:
- Combined use of infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations.
- Analysis of spectral features in the 1000-1350 cm(-1) and above 1350 cm(-1) regions.
- Topological mapping of the cluster potential energy landscape.
Main Results:
- Identified three distinct structural motifs: canonical (charge-solvated), zwitterionic (charge-separated), and TMA-bridged.
- Observed similar product channels (TMA·H(+) and 3-CF3-Phe·H(+)) in the 1000-1350 cm(-1) region.
- Demonstrated mode-specific dissociation: charge-solvated structures yield protonated TMA, while zwitterionic/TMA-bridged structures yield protonated 3-CF3-Phe above 1350 cm(-1).
Conclusions:
- Proposed mechanisms for isomerization and mode-selective dissociation.
- Highlighted the role of IR-induced isomerization in cluster transparency and deactivation of dissociation channels.
- Established a structure-dependent fragmentation mechanism for the studied dimer.
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