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Avidin-Biotin Complex (ABC) Methods

The ABC method incorporates a large glycoprotein called avidin that has a very high affinity for a low molecular weight vitamin called biotin. Avidin can be labeled with peroxidase or fluorescein. Biotin can be conjugated to antibodies. The technique methodology consists of using an unlabeled primary antibody, a biotinylated secondary antibody, and a complex of avidin-biotin peroxidase. The peroxidase is then developed by the DAB or other substrates to produce a colored label. This method is a little more time consuming especially if you are mixing all of your reagents. Fortunately, there are companies that produce kits with the blocking, secondary, and the link reagents already prepared or are concentrates that the technologist dilutes.