Figure 1b: (Reaction Description: Conjugation of Horseradish Peroxidase (HRPO) to antibody (IgG) using the periodate oxidation method. The method involves three chemical steps: (1) sodium periodate (NaIO4) oxidation of the carbohydrate side chains of HRPO, (2) Schiff base formation between activated peroxidase and amino groups of the antibody, and (3) sodium borohydride (NaBH4) reduction of the Schiff base to form a stable conjugate. Contributed by Scott E. Winston, Steven A. Fuller, Michael J. Evelegh, and John G.R. Hurrell Current Protocols in Molecular Biology (2000) 11.1.1-11.1.).