title: Structure, stability, and ligand exchange of copper(II) complexes with oxidized glutathione.
abstract: Formation constants and structures of copper(II) complexes with oxidized glutathione (L) have been determined by computer modelling of spectrophotometric and NMR relaxation measurements data over a wide range of pH (1-13) and metal and ligand concentrations in aqueous KNO(3) (1M) at 298K. Among 11 found complexes, four forms were characterized for the first time. Based on a comparison of thermodynamic, relaxation, and optical and EPR spectroscopy parameters the structural conclusions were made. In particular, the CuLH(2) and CuLH(-) complexes both contain two isomers which are similar to mono- and bis-aminoacid copper(II) complexes. In the Cu(2)L and Cu(3)L(2)(2-) species one of the copper atoms is bound only with the carboxylate or carbonyl groups and the others are coordinated similarly to aminoacid chelates. Along with the last, in Cu(2)LH(-2)(2-) two bridging OH(-) groups in one isomer or two chelate rings including deprotonated peptide nitrogen and glycinyl carboxylate oxygen in another are also present. In Cu(3)L(2)H(-4)(6-) the mixed variant of coordination between CuL(2-) (CuN(2)O(2)) and Cu(2)LH(-4)(4-)(CuN(3)O) is realized. The structures of polynuclear complexes have been optimized in density functional theory computations. Rate constants of ligand exchange reactions of Cu(LH)(2)(4-) and CuL(2)(6-) with participation of the LH(3-) and L(4-) forms were determined for the first time. Factors determining rates of these processes have been revealed and their proceeding by associative substitution mechanism shown.
authors.affiliation: Department of Inorganic Chemistry, Kazan State University, Kremlevskaya st. 18, Kazan 420008, Russian Federation. valery.shtyrlin@ksu.ru <valery.shtyrlin@ksu.ru>
authors.forename: Valery G
authors.initials: VG
authors.lastname: Shtyrlin
authors.forename: Yulia I
authors.initials: YI
authors.lastname: Zyavkina
authors.forename: Vladislav S
authors.initials: VS
authors.lastname: Ilakin
authors.forename: Ruslan R
authors.initials: RR
authors.lastname: Garipov
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Zakharov