Comparison of three conjugation procedures for the formation of tracers for use in enzyme immunoassays.

One of the requirements for enzyme immunoassay is the formation of a labelled component of the assay system which can be either the ligand or the binder. Three methods for conjugating alkaline phosphatase to human placental lactogen were investigated, involving water-soluble carbodiimide, glutaraldehyde, and the periodate oxidation technique. Of the 3, the periodate oxidation technique proved superior giving a conjugate with only slight changes in the Michaelis constant (Km) and maximum velocity (Vmax) which could be used for an enzyme immunoassay for human placental lactogen in human plasma.