Description; Application; BCIP®/NBT-Purple Liquid Substrate System for Membranes has been used as a substrate for alkaline phosphatase • for the detection of secondary antibodies by immunoblot[1] • in ELISPOT assay[2] • in dot blot analysis[3] • in western blot to visualize protein bands on nitrocellulose membrane[4]; Biochem/physiol Actions; 5-bromo-4-chloro-3-indolyl phosphate (BCIP)/ nitro blue tetrazolium (NBT) is a chromogenic substrate system for the detection of alkaline phosphatase (AP) enzyme. AP hydrolyses BCIP to form an intermediate leucoindigo compound and is further oxidized by NBT to form 5,5′-dibromo-4,4′-dichloro indigo (BCI). NBT is reduced to an insoluble purple diformazan (DF) and forms NBT-DF. A mixture of NBT-DF and BCI results in the dark purple colored precipitate. AP by hydrolysing many BCIP molecules makes it a highly sensitive method.[4]; Caution; Stable at least one year at 2-8 °C.; Physical form; Ready-to-use.; Legal Information; BCIP is a registered trademark of Sigma-Aldrich Co. LLC