title: Alkali-Metal-Ion-Assisted Hydrogen Atom Transfer in the Homocysteine Radical.
abstract: Intramolecular hydrogen atom transfer (HAT) was examined in homocysteine (Hcy) thiyl radical/alkali metal ion complexes in the gas phase by combination of experimental techniques (ion-molecule reactions and infrared multiple photon dissociation spectroscopy) and theoretical calculations. The experimental results unequivocally show that metal ion complexation (as opposed to protonation) of the regiospecifically generated Hcy thiyl radical promotes its rapid isomerisation into an α-carbon radical via HAT. Theoretical calculations were employed to calculate the most probable HAT pathway and found that in alkali metal ion complexes the activation barrier is significantly lower, in full agreement with the experimental data. This is, to our knowledge, the first example of a gas-phase thiyl radical thermal rearrangement into an α-carbon species within the same amino acid residue and is consistent with the solution phase behaviour of Hcy radical.
authors.affiliation: Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lesslie
authors.affiliation: Department of Chemistry and Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, M3J 1P3, Canada.|Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
authors.forename: Justin Kai-Chi
authors.initials: JK
authors.lastname: Lau
authors.affiliation: Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA.
authors.forename: John T
authors.initials: JT
authors.lastname: Lawler
authors.affiliation: Department of Chemistry and Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, M3J 1P3, Canada.|Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.
authors.forename: K W Michael
authors.initials: KW
authors.lastname: Siu
authors.affiliation: Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7c, 6525, ED Nijmegen, The Netherlands.
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.affiliation: Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7c, 6525, ED Nijmegen, The Netherlands.
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.affiliation: Department of Chemistry and Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, M3J 1P3, Canada. ach@yorku.ca.
authors.forename: Alan C
authors.initials: AC
authors.lastname: Hopkinson
authors.affiliation: Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, 60115, USA. ryzhov@niu.edu.
authors.forename: Victor
authors.initials: V
authors.lastname: Ryzhov
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006710:Homocysteine / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008672:Metals, Alkali / Q000737:chemistry*; D008958:Models, Molecular; D011789:Quantum Theory
chemical_list: D000596:Amino Acids; D005609:Free Radicals; D008672:Metals, Alkali; D006710:Homocysteine; D006859:Hydrogen
keywords: alkali metal ions; homocysteine; hydrogen transfer; ion-molecule reactions; radical ions