title: Infrared multiple-photon dissociation spectroscopy of tripositive ions: lanthanum-tryptophan complexes.
abstract: Collision-induced charge disproportionation limits the stability of triply charged metal ion complexes and has thus far prevented successful acquisition of their gas-phase IR spectra. This has curtailed our understanding of the structures of triply charged metal complexes in the gas phase and in biological environments. Herein we report the first gas-phase IR spectra of triply charged La(III) complexes with a derivative of tryptophan (N-acetyl tryptophan methyl ester), and an unusual dissociation product, a lanthanum amidate. These spectra are compared with those predicted using density functional theory. The best structures are those of the lowest energies that differ by details in the π-interaction between La(3+) and the indole rings. Other binding sites on the tryptophan derivative are the carbonyl oxygens. In the lanthanum amidate, La(3+) replaces an H(+) in the amide bond of the tryptophan derivative.
authors.affiliation: Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Udo H
authors.initials: UH
authors.lastname: Verkerk
authors.forename: Junfang
authors.initials: J
authors.lastname: Zhao
authors.forename: Irine S
authors.initials: IS
authors.lastname: Saminathan
authors.forename: Justin Kai-Chi
authors.initials: JK
authors.lastname: Lau
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Alan C
authors.initials: AC
authors.lastname: Hopkinson
authors.forename: K W Michael
authors.initials: KW
authors.lastname: Siu
mesh_terms: D007811:Lanthanum / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D017785:Photons; D013055:Spectrophotometry, Infrared; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D007811:Lanthanum; D014364:Tryptophan