title: Structure and reactivity of homocysteine radical cation in the gas phase studied by ion-molecule reactions and infrared multiple photon dissociation.
abstract: The reactivity of the cysteine (Cys) and homocysteine (Hcy) radical cation was studied using ion-molecule reactions. The radical cations were generated via collision-induced dissociation (CID) of their S-nitrosylated precursors. Cleavage of the S-NO bond led to the formation of the radical initially positioned on the sulfur atom. The reactions of the radical cations with dimethyl disulfide revealed that the cysteine radical cation reacts more quickly than the homocysteine radical cation. Infrared multiple photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations were used to determine the structure of the homocysteine radical cation, which was compared to the previously published structure of the cysteine radical cation (Sinha et al. Phys. Chem. Chem. Phys. 2010, 12, 9794-9800). IRMPD spectroscopy and DFT calculations revealed that this difference in radical reactivity was not a result of a radical rearrangement for the homocysteine radical cation but rather that the reactivity was modulated by stronger hydrogen bonding.
authors.affiliation: Department of Chemistry and Biochemistry, and Center for Biochemical and Biophysical Studies, Northern Illinois University, Dekalb, Illinois 60115, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: Osburn
authors.forename: Ticia
authors.initials: T
authors.lastname: Burgie
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Richard A J
authors.initials: RA
authors.lastname: O'Hair
authors.forename: Victor
authors.initials: V
authors.lastname: Ryzhov
mesh_terms: D005609:Free Radicals / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D006710:Homocysteine / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D015394:Molecular Structure; D017785:Photons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared
chemical_list: D005609:Free Radicals; D005740:Gases; D007477:Ions; D006710:Homocysteine