ABSTRACT
The interaction of the VO2+ cation with homocysteine was investigated by electron absorption spectroscopy in aqueous solution at different metal-to-ligand ratios. The direct reduction of vanadate(V) solutions with homocysteine was also investigated. The results suggest that the interaction is different from that found in the case of cysteine and occurs through pairs of amino and carboxylate groups of the amino acid. The interaction of VO2+ with homocystine, the oxidation product of homocysteine, was also analyzed. The interest of the results in relation to vanadium metabolism and detoxification is briefly discussed.
Subject(s)
Homocysteine/metabolism , Vanadates/chemistry , Vanadates/metabolism , Amino Acids/chemistry , Cations , Cysteine/chemistry , Electrons , Homocysteine/chemistry , Hydrogen-Ion Concentration , Ligands , Metals/chemistry , Models, Chemical , Spectrophotometry , Trace ElementsABSTRACT
The interaction of sodium metavanadate and VOCl3 with ascorbic acid, one of the possible natural reducing agents of vanadium(V) to oxovanadium(IV), has been investigated. Three new VO2+ complexes could be isolated as microcrystalline powders. One of them, of composition K1.5Na0.5[VO(HAsc)(OH)3], contains ascorbic acid as a monodentate ligand. In the other two, K[VO(Diketo)(OH)] x H2O and Na3[VO(Diketo)2(OH)], the enolized form of 2,3-diketogulonic acid (one of the oxidation products of ascorbic acid), acts as a bidentate ligand. The complexes were characterized by means of electronic (absorption and reflectance) and infrared spectroscopy and magnetic susceptibility measurements. Their thermal behavior was investigated by thermogravimetric and differential thermal analyses. The interest of the investigated system in relation to vanadium detoxification is also discussed.
Subject(s)
Ascorbic Acid/chemistry , Vanadates/chemistry , Electrochemistry , Indicators and Reagents , Photometry , Spectroscopy, Fourier Transform InfraredABSTRACT
A new VO2+ complex with salicylic acid acetate (Aspirin) of formula C18H18Cl2O12V2 was synthesized and characterized. Its biological effects upon cell proliferation, differentiation and promotion of tyrosine protein phosphorylation have been tested in two lines of osteoblast-like cells in culture.
Subject(s)
Aspirin/chemical synthesis , Vanadates/chemical synthesis , Animals , Aspirin/pharmacology , Blotting, Western , Bone and Bones/metabolism , Cell Differentiation/drug effects , Cell Division/drug effects , Cells, Cultured , Humans , Osteoblasts/drug effects , Phosphorylation , Phosphotyrosine/metabolism , Spectrophotometry, Infrared , Vanadates/pharmacologyABSTRACT
The interaction between the VO2+ cation and cystine was investigated by electron absorption spectroscopy in aqueous solutions at different metal-to-ligand ratios. Reduction of NaVO3 solutions with cysteine gave similar spectra. The results suggest that interaction occurs through the carboxylate and amino groups of the ligand. The interest of the results in relation to vanadium metabolism are commented upon.
Subject(s)
Cystine/chemistry , Cations , Oxidation-Reduction , Spectrum Analysis/methodsABSTRACT
The interaction of the vanadyl (IV) (VO2+) cation with carnosine (the dipeptide beta-alanyl-histidine) has been investigated by electron absorption spectroscopy at high ligand-to-metal ratios and at different pH values. The results show that in the range 6.0-8.5, the cation interacts with the imidazole group of four different carnosine molecules and points to the presence of an axially coordinated water molecule. These suppositions were confirmed by the behavior of the VO2+/imidazole system, which was investigated under similar experimental conditions, and supported by previous ENDOR (electron-nuclear double resonance) results. The study was complemented with additional measurements using the glycylglycine, glycylglycine/imidazole, and histidine systems as ligands.
Subject(s)
Carnosine/chemistry , Glycylglycine/chemistry , Histidine/chemistry , Vanadates/chemistry , Hydrogen-Ion Concentration , Imidazoles , Ligands , Magnetic Resonance Spectroscopy , SpectrophotometryABSTRACT
The interaction of the vanadyl(IV) cation with oxidized glutathione (GSSG) in solution has been investigated using spectrophotometric techniques. Two complexes, stable at different metal-to-ligand ratios, could be identified at pH = 7. A solid 2:1 VO2+:GSSG complex could also be isolated at pH = 4.5 and characterized by chemical analysis and infrared and electronic spectroscopies. Its thermal behavior was investigated through TG and DTA measurements.
Subject(s)
Glutathione/analogs & derivatives , Vanadates/chemistry , Glutathione/chemistry , Glutathione Disulfide , Solutions , Spectrophotometry , Spectrophotometry, InfraredABSTRACT
The interaction of the vanadyl (IV) cation with reduced glutathione (GSH) has been investigated by electronic absorption spectroscopy, at different metal-to-ligand ratios and pH values. The interaction depends strongly on the initial VO2+/GSH ratio. Starting with a tenfold GSH excess, coordination takes place through the two carboxylate groups of the ligand, generating (at pH = 7) a blue 1:2 VO2+/GSH complex; this stoichiometry could be confirmed by photometric titration experiments. Higher GSH concentrations produce a violet complex, which can also be obtained by addition of GSH to the blue species. Some measurements with the three component amino acids of GSH, as well as results obtained from the VO3-/GSH system, allowed a wider insight into the characteristics of this violet complex, in which the cation interacts with S and N atoms of the peptide.
