Preparation of phosphorylcholine-conjugated antigens

In response to the need for a phosphorylcholine (PC) hapten that could be attached easily to carrier molecules, synthesis of PC-carrier conjugates was undertaken. An isothiocyanate-PC derivative was prepared by mixing p-aminophenyl-PC with thiophosgene. The isothiocyanate-PC derivative was coupled directly to aminoethylated Ficoll at room temperature in a bicarbonate buffer. Maximum coupling, 31 PC groups per Ficoll molecule, occurred within 16 h. The number of PC per Ficoll was determined spectrophotometrically at 245 nm. This approach was also successively used for conjugating PC to bovine serum albumin and aminoethylated Sepharose.