Mode-specific fragmentation of amino acid-containing clusters.
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.
Department of Chemistry, University of Waterloo, Waterloo, ON, CanadaN2L 3G1. shopkins@uwaterloo.ca mcmahon@uwaterloo.ca.
W Scott
WS
Hopkins
Department of Chemistry, University of Waterloo, Waterloo, ON, CanadaN2L 3G1. shopkins@uwaterloo.ca mcmahon@uwaterloo.ca.
Rick A
RA
Marta
Laboratoire Chimie Physique - CLIO, Bâtiment 201, Porte 2, Campus Universitaire d'Orsay, Orsay, 91405, France.
Vincent
V
Steinmetz
Department of Chemistry, University of Waterloo, Waterloo, ON, CanadaN2L 3G1. shopkins@uwaterloo.ca mcmahon@uwaterloo.ca.
Terry B
TB
McMahon
D000596:Amino Acids / Q000737:chemistry*; D007536:Isomerism; D008744:Methylamines / Q000737:chemistry; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000737:chemistry; D017785:Photons; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics
C557397:4-(trifluoromethyl)phenylalanine; D000596:Amino Acids; D008744:Methylamines; D010649:Phenylalanine; C023336:trimethylamine