title: Collision-induced dissociation of halide ion-arginine complexes: evidence for anion-induced zwitterion formation in gas-phase arginine.
abstract: We report the first low-energy collisional-induced dissociation studies of the X(-)·arginine (X(-) = F(-), Cl(-), Br(-), I(-), NO(3)(-), ClO(3)(-)) series of clusters to investigate the novel phenomenom of anion-induced zwitterion formation in a gas-phase amino acid. Fragmentation of the small halide ion clusters (F(-)·arginine and Cl(-)·arginine) is dominated by deprotonation of the arginine, whereas the major fragmentation channel for the largest ion clusters (I(-)·arginine and ClO(3)(-)·arginine) corresponds to simple cluster fission into the ion and neutral molecule. However, the fragmentation profiles of Br(-)·arginine and NO(3)(-)·arginine, display distinctive features that are consistent with the presence of the zwitterionic form of the amino acid in these clusters. The various dissociation pathways have been studied as a function of % collision energy and are discussed in comparison to the fragmentation profiles of protonated and deprotonated arginine. Electronic structure calculations are presented for Br(-)·arginine to support the presence of the zwitterionic amino acid in this complex. The results obtained in this work provide important information on the low-energy potential energy surfaces of these anion-amino acid clusters and reveal the presence of several overlapping surfaces in the low-energy region for the Br(-)·arginine and NO(3)(-)·arginine systems.
authors.affiliation: Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Milner
authors.forename: Michael G D
authors.initials: MG
authors.lastname: Nix
authors.forename: Caroline E H
authors.initials: CE
authors.lastname: Dessent
mesh_terms: D000838:Anions / Q000737:chemistry; D001120:Arginine / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D006219:Halogens / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D000838:Anions; D005740:Gases; D006219:Halogens; D009566:Nitrates; D001120:Arginine