Reaction of reduced disulfide bonds in α-lactalbumin and β-lactoglobulin with acrylonitrile

Abstract Reduction of disulfide bonds of α-lactalbumin and β-lactoglobulin with β-mercaptoethanol and subsequent reaction with acrylonitrile was shown to be specific and was confined to the thiol groups, as determined by total amino acid analysis of the protein derivatives. The reaction results in the quantitative and specific conversion of the cysteinyl residues to S -cyanoethylcysteinyl groups. Upon acid hydrolysis, the S -cyanoethylcysteinyl groups were converted quantitatively to S -carboxyethylcysteine and were determined analytically as such.