title: Spectroscopic and potentiometric study of the SOD mimic system copper(II)/acetyl-L-histidylglycyl-L-histidylglycine.
abstract: Stoichiometry, stability constants and solution structures of the copper(II) complexes of the N-acetylated tetrapeptide HisGlyHisGly were determined in aqueous solution in the pH range 2-11. The potentiometric and spectroscopic data (UV-Vis, CD, EPR and Raman scattering) show that acetylation of the amino terminal group induces drastic changes in the coordination properties of AcHGHG compared to HGHG. The N3 atoms of the histidine side chains are the first anchoring sites of the copper(II) ion. At pH 4.7 and 5.6 both the imidazole rings cooperate in the formation of a 2N equatorial set, while, at higher pH values, 3N and 4N complexes are formed through the coordination of peptide N- atoms. The logbeta values of the copper complexes of AcHGHG are by far lower than those of the corresponding species in the parent CuII-HGHG system.
authors.affiliation: Dipartimento di Chimica and Istituto di Chimica dei Composti Organo Metallici del C.N.R., Università di Siena, Pian dei Mantellini 44, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Casolaro
authors.forename: Mario
authors.initials: M
authors.lastname: Chelli
authors.forename: Mauro
authors.initials: M
authors.lastname: Ginanneschi
authors.forename: Franco
authors.initials: F
authors.lastname: Laschi
authors.forename: Luigi
authors.initials: L
authors.lastname: Messori
authors.forename: Maurizio
authors.initials: M
authors.lastname: Muniz-Miranda
authors.forename: Anna M
authors.initials: AM
authors.lastname: Papini
authors.forename: T
authors.initials: T
authors.lastname: Kowalik-Jankowska
authors.forename: Henryk
authors.initials: H
authors.lastname: Kozlowski
mesh_terms: D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008968:Molecular Conformation; D018716:Molecular Mimicry; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000378:metabolism*; D011199:Potentiometry; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman; D013482:Superoxide Dismutase / Q000378:metabolism*; D013696:Temperature
chemical_list: D009842:Oligopeptides; C460941:acetyl-histidylglycyl-histidylglycine; D003300:Copper; D013482:Superoxide Dismutase