DAB Substrates

DAB (3,3'-Diaminobenzidine) is a water-soluble, chromogenic substrate of horseradish peroxidase (HRP), a common label conjugated to antibodies. HRP catalyzes the oxidation of DAB by hydrogen peroxide. The result is a brown precipitate that localizes to the sites of HRP-bound antibodies. This precipitate is also insoluble in alcohol and can be used with alcohol-soluble counterstains. Green or red colored counterstains may provide good viewing contrast for DAB’s brown color. DAB is commonly used in applications involving protein or antigen detection, including immunohistochemistry, immunocytochemistry, Western blot, and in situ hybridization.