This CF?640R tyramide conjugate is used for tyramide signal amplification (TSA)1,2,3, which is an enzyme-mediated detection method that uses horseradish peroxidase (HRP) to generate high-density labeling of a target protein or nucleic acid in situ. A tyramide conjugate is incubated in the presence of HRP (often bound to a secondary antibody), which catalyzes the binding of the tyramide (and associated label) to adjacent tyrosines for enhanced fluorescent signal. CF?640R is a novel rhodamine-based dye spectrally very similar to Cy?5 and Alexa Fluor? 647. CF?640R is much brighter than Cy?5 and at least as bright as Alexa Fluor? 647 when excited at 633 or 635 nm. However, the most important advantage of CF?640R is its exceptional photostability. CF?640R is far more photostable than the cyanine-based dyes Cy?5 and Alexa Fluor? 647. It is also more photostable than Atto 647N, a dye that has been extensively used in single molecule-based imaging.