Almost every immunoassay incorporates at least one reagent that is derived from the synthesis of a bioconjugate.'12 Bioconjugates, such as immunogens'.2 and enzyme conjugates3, are usually prepared by direct coupling of carboxylic acid haptens to proteins using EDAC4 (ethyl dimethylaminopropylcarbodiimide) or DCC' (dicyclohexylcarbodiimide). This process, however, leads to undesired side reactions such as cross- linking of the protein, ...
