Tyramide signal amplification is an enzyme-mediated detection method that uses the catalytic activity of horseradish peroxidase (HRP) to generate high-density labeling of a target protein or nucleic acid sequence in situ. The TSA Kit #40 includes HRP—goat anti—mouse IgG and our bright, orange-fluorescent Alexa Fluor 555 tyramide (which is spectrally similar to Cy3 dye).