Fast Red TR salt chromogen

The Fast Red TR salt chromogen for use with alkaline phosphatase... 

This reporter is obviously encountered in the APAAP technique, but it can also be conjugated to biotin and used successfully in the ABC methods. The enzyme is sourced from calf intestine, this form being resistant to the blocking effect of levamisole, which is added to the substrate buffer and blocks all other types of endogenous alkaline phosphatase activity. Several chromogens can be used, the most popular being Fast Red TR salt which yields a bright red alcohol soluble reaction product (34). 

This can be used in its acid form or as the sodium salt. The chromogens Fast Red TR and Fast Blue BB produce a bright red or blue end product, respectively. Both are soluble in alcoholic and other organic solvents, so aqueous mounting media must be used. Fast Red TR is preferred when staining cell smears. 

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