Ascorbic acid reaction with disulphide compounds: effects and applications

A method was developed for estimation of concentrations of cystine based on the reaction of this oxidised amino acid with ascorbic acid and copper ion . The standard curve which was constructed was used as the basis for invest igation of the effects which both cystine and glutathione disulphide, and s ome disulphide proteins, exerted on the amount of hydrogen peroxide formed in the reaction of ascorbic acid. The hydrogen peroxide product was lowered in the presence of the disulphide compounds. The disulphide compounds also lowered the amount of deoxyribose reacting material formed during the asco rbic acid oxidation. The reaction between ascorbic acid and copper and cyst ine was used to estimate the amount of the disulphide amino acid in acid di gests of proteins. (C) 2000 Elsevier Science B.V. All rights reserved.