ImmunoTek(TM) BCIP Stable Liquid Substrate 2.31mM BCIP, , BCIP is an excellent substrate for alkaline phosphatase (AP). Upon hydrolysis of the phosphate ester by AP, the resulting halogenated indigo polymerizes to an insoluble blue dimer at the site(s) of enzyme activity. When reacted with alkaline phosphatase, the free halogenated indolyl derivative dimerizes forming an insoluble blue indigo dye. This product is useful for immunoblotting and immunohistochemical procedures as well as in situ hybridization. Thus BCIP is an excellent substrate for membrane based assays where a blue endpoint is desired. United States Biological provides a stable BCIP solution that has been proven useful for detection of AP probes using a variety of blotting techniques.