TSA involves horseradish peroxidase

TSA involves horseradish peroxidase (HRP)-catalyzed deposition of tyramide on and near a target protein or nucleic acid sequence in situ. In the presence of low concentrations of H O , HRP is able to convert a labeled tyramide substrate into a highly reactive form that can covalently bind to tyrosine residues on proteins at or near the HRP. This generates high density tyramide labeling and is the reason for the exceptional sensitivity of this system. Tyramide can be labeled with a fluorophore or a hapten (such as biotin or DNP). Because the label is covalently linked to the sample, the antibodies can be stripped off without affecting signal.This allows multiple rounds of staining with antibodies from the same host species for multiplex detection.