title: Optical and structural properties of copper-oxytocin dications in the gas phase.
abstract: We present a joint experimental and theoretical investigation of the structural and optical properties of copper-oxytocin dications in the gas phase. Ion mobility and UV photodissociation experiments were performed, allowing the investigation of the influence of the Cu(2+) ion on the structural and optical properties of oxytocin. Density functional theory calculations were performed to find low energy structures for the bare and complexed peptide and to characterize optical spectral features. Copper complexation induces a drastic change in the structure of the oxytocin peptide. In particular, we predict a 4N chelation of the copper cation which leads to a contraction of the oxytocin ring. The gas phase lowest-energy structures are compared with the X-ray crystal structure of the oxytocin molecule bound to its receptor protein. The optical spectrum of oxytocin complexed with the copper cation displays a global enhancement of the photofragmentation yield as compared to the one recorded for the doubly protonated oxytocin. Moreover, experimental and calculated optical spectra of protonated tyrosine have also been determined, since its leading features are present in oxytocin as well.
authors.affiliation: Université de Lyon, F-69622, Lyon, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Joly
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Antoine
authors.forename: Florian
authors.initials: F
authors.lastname: Albrieux
authors.forename: Renaud
authors.initials: R
authors.lastname: Ballivian
authors.forename: Michel
authors.initials: M
authors.lastname: Broyer
authors.forename: Fabien
authors.initials: F
authors.lastname: Chirot
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lemoine
authors.forename: Philippe
authors.initials: P
authors.lastname: Dugourd
authors.forename: Claudio
authors.initials: C
authors.lastname: Greco
authors.forename: Roland
authors.initials: R
authors.lastname: Mitrić
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bonacić-Koutecký
mesh_terms: D002413:Cations, Divalent; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005740:Gases; D015394:Molecular Structure; D010121:Oxytocin / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D005740:Gases; D010121:Oxytocin; D003300:Copper