title: Structural characterization of gas-phase cysteine and cysteine methyl ester complexes with zinc and cadmium dications by infrared multiple photon dissociation spectroscopy.
abstract: Structural characterization of gas-phase ions of cysteine (Cys) and cysteine methyl ester (CysOMe) complexed to zinc and cadmium is investigated by infrared multiple photon dissociation (IRMPD) action spectroscopy using a free electron laser in combination with density functional theory calculations. IRMPD spectra are measured for [Zn(Cys-H)](+), [Cd(Cys-H)](+), [Zn(CysOMe-H)](+), [Cd(CysOMe-H)](+) and CdCl(+)(CysOMe) and are accompanied by quantum mechanical calculations of the predicted linear absorption spectra at the B3LYP/6-311+G(d,p) (Zn(2+) complexes) and B3LYP/def2TZVP levels (Cd(2+) complexes). On the basis of these experiments and calculations, the conformation that best reproduces the IRMPD spectra for the complexes of the deprotonated amino acids, [M(Cys-H)](+) and [M(CysOMe-H)](+), is a charge-solvated (CS) tridentate structure where the metal dication binds to the amine and carbonyl groups of the amino acid backbone and the deprotonated sulfur atom of the side chain, [N,CO,S(-)]. The intact amino acid complex, CdCl(+)(CysOMe) binds in the equivalent motif [N,CO,S]. These binding motifs are in agreement with the predicted ground structures of these complexes at the B3LYP, B3LYP-GD3BJ (with empirical dispersion corrections), B3P86, and MP2(full) levels.
authors.affiliation: Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA. armentrout@chem.utah.edu.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Coates
authors.forename: Christopher P
authors.initials: CP
authors.lastname: McNary
authors.forename: Georgia C
authors.initials: GC
authors.lastname: Boles
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: P B
authors.initials: PB
authors.lastname: Armentrout
mesh_terms: D002104:Cadmium / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry; D007259:Infrared Rays; D008958:Models, Molecular; D017785:Photons; D021241:Spectrometry, Mass, Electrospray Ionization; D015032:Zinc / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D002104:Cadmium; D015032:Zinc; D003545:Cysteine; C017507:mecysteine