title: The systems V(IV)O(2+)-glutathione and related ligands: a potentiometric and spectroscopic study.
abstract: The equilibria in the system V(IV)O(2+)-glutathione in aqueous solution were studied in the pH range 2-11 by a combination of pH-potentiometry and spectroscopy (EPR, visible absorption and circular dichroism). The results of the various methods are consistent and the equilibrium model includes the species MLH(3), MLH(2), MLH, ML(2)H(2), MLH(-1), and MLH(-2) and several hydrolysis products (where H(4)L denotes totally protonated glutathione); individual formation constants and spectra are given. ML(2)H(2) is the predominant species at physiological pH. Plausible structures for each stoichiometry are discussed. The related V(IV)O(2+) systems of S-methylglutathione and gamma- L-glutamyl- L-cysteinyl ethyl ester were studied by means of the same spectroscopic techniques in order to support the established binding modes for the glutathione complexes. The importance of glutathione and oxidized glutathione in binding V(IV)O(2+) in cells is assessed.
authors.affiliation: Centro Química Estrutural, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal. pcjpessoa@popsrv.ist.utl.pt
authors.forename: João Costa
authors.initials: JC
authors.lastname: Pessoa
authors.forename: Isabel
authors.initials: I
authors.lastname: Tomaz
authors.forename: Tamás
authors.initials: T
authors.lastname: Kiss
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Kiss
authors.forename: Péter
authors.initials: P
authors.lastname: Buglyó
mesh_terms: D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry*; D019803:Glutathione Disulfide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D011199:Potentiometry; D013057:Spectrum Analysis; D014638:Vanadates / Q000737:chemistry*
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D014638:Vanadates; C042431:S-ethyl glutathione; D005978:Glutathione; C017514:S-methyl glutathione; D019803:Glutathione Disulfide