3773-07-7Relevant academic research and scientific papers
Direct electrochemical oxidation of disulfides at anodically pretreated boron-doped diamond electrodes
Terashima,Rao, Tata N.,Sarada,Kubota,Fujishima
, p. 1564 - 1572 (2003)
Anodically oxidized diamond electrodes have been used to oxidize disulfides, thiols, and methionine in aqueous acidic media and tested for amperometric detection of these compounds after chromatographic separation. Cyclic voltammetric signals for 1 mM glutathione disulfide (GSSG) were observed at 1.39 and 1.84 V vs SCE, the values being less positive than those of its as-deposited counterpart as well as glassy carbon electrode. The voltammetric and chronocoulometric results have indicated the high stability of the electrode with negligible adsorption. A positive shift in the peak potential with increasing pH indicated the attractive electrostatic interaction between the anodically oxidized diamond surface and the positively charged GSSG in acidic media that promoted its analytical performance. The results of the electrolysis experiments of disulfides and thiols showed that the oxidation reaction mechanism of glutathione (GSH) and GSSG involves oxygen transfer. Following separation by liquid chromatography (LC), the determination of both GSH and GSSG in rat whole blood was achieved at a constant potential (1.50 V vs Ag/AgCl), and the limits of detection for GSH and GSSG were found to be 1.4 nM (0.028 pmol) and 1.9 nM (0.037 pmol) with a linear calibration range up to 0.25 mM. These detection limits were much lower than those reported for the amperometry using Bi-PbO2 electrodes and LC-mass spectrometry, and the LC method using diamond electrodes were comparable with enzymatic assay in real sample analysis. The high response stability and reproducibility together with the possibility of regeneration of the electrode surface by on-line anodic treatment at 3 V for 30 min further support the applicability of anodically pretreated diamond for amperometric detection of disulfides.
Kinetics and mechanism of the reactions of superoxochromium(III) ion with biological thiols
Perez-Benito, Joaquin F.,Arias, Conchita
, p. 5837 - 5845 (2007/10/03)
The kinetics of the oxidation of three biological thiols (L-cysteine, glutathione, and DL-penicillamine) to their sulfinic and sulfonic acid derivatives by CrOO2+ in aqueous perchloric acid and in the presence of 2-propanol have been studied spectrophotometrically with the aid of the initial-rates method. The kinetic order of the oxidant is 2, whereas that of the reductant is not defined. The acidity of the medium has a slight effect on the initial rates (acid catalysis for both L-cysteine and DL-penicillamine and base catalysis for glutathione). An increase of the ionic strength leads to a rise of the initial rate for both L-cysteine and DL-penicillamine, whereas the initial rate for glutathione is insensitive to the ionic strength. The reactions are inhibited by both 2-propanol and dissolved O2 and catalyzed by Mn2+, whereas Ce3+ has almost no effect on them. At low 2-propanol concentration and in the absence of Mn2+ the initial rate vs temperature plots have a minimum at around 20 °C, whereas in the presence of either concentrated 2-propanol or Mn2+ the Arrhenius law is fulfilled. A single mechanism is proposed for the three reactions involving a CrOO2+/thiol complex, CrOOH2+, and CrO2+ as intermediates. The bimolecular rate constants for the reactions of the intermediate CrO2+ with L-cysteine and DL-penicillamine at 25.0 °C have been obtained (around 103 M-1 s-1 in both cases). Some kinetic data for the decomposition of CrOO2+ in the absence of thiol are also given.
Oxidative Cleavage of Peptide and Protein Disulphide Bonds by Gold(III): a Mechanism for Gold Toxicity
Witkiewicz, Patricia L.,Shaw, C. Frank
, p. 1111 - 1114 (2007/10/02)
The oxidative cleavage of disulphide bonds to form the sulphonic acid derivatives is shown to be an important reaction of AuX4- (X = Cl, Br) with proteins and peptides; the implications of this reaction for the toxicity of gold compounds are discussed.
