CONJUGATION OF SYNTHETIC PEPTIDES TO PROTEINS - QUANTITATION FROM S-CARBOXYMETHYLCYSTEINE RELEASED UPON ACID-HYDROLYSIS

A method described here for conjugating synthetic peptides to carrier proteins provides a convenient method for determining peptide-to-carrier protein rations. N-Bromoacetyl-containing peptides are reacted in situ with carrier proteins in which the disulfide bonds were reduced with tri-n-butylphosphine. At pH 7-8 and ambient temperature, the newly formed sufhydryl groups of the carrier protein react exclusively with the bromoacetyl moiety of the peptide to form conjugates having stable thio ether linkages. Acid hydrolyses of these conjugates release S-carboxymethylcysteine in amounts proportional to the amounts of peptides conjugated and thus allow determination of peptide-to-protein ratios. © 1990.