X-Gal is a well known histochemical substrate used to detect the ß-galactosidase enzyme (1, 2, 3, 4, 9, 10). Identification of lacf-colonies (8). X-gal is used to distinguish recombinant plasmids from parental vectors in cloning experiments using vectors containing the lacZ or lacZ [DMvP1](-)peptide gene (2, 3, 5). Upon hydrolysis, X-Gal yields a localized, insoluble blue precipitate making it exceptionally useful in blotting, immunocytochemical, and ELISA assays. X-Gal has been used for the detection of coliforms (E. coli) in municipal water supplies (6) and food products (7). X-Gal is often used in conjunction with IPTG (Isopropyl-ß-D-thiogalactopyranoside, cat. no. 26600) which binds and inhibits the lac repressor thus inducing ß-galactosidase activity.Stock solution: 20 mg/ml in DMF. Store in aliquots at -20 °C in the dark. For detection of transformants, use in final concentration of 40 µg/ml. X-Gal is a well known histochemical substrate used to detect the ß-galactosidase enzyme (1, 2, 3, 4, 9, 10). Identification of lacf-colonies (8). X-gal is used to distinguish recombinant plasmids from parental vectors in cloning experiments using vectors containing the lacZ or lacZ [DMvP1](-)peptide gene (2, 3, 5). Upon hydrolysis, X-Gal yields a localized, insoluble blue precipitate making it exceptionally useful in blotting, immunocytochemical, and ELISA assays. X-Gal has been used for the detection of coliforms (E. coli) in municipal water supplies (6) and food products (7). X-Gal is often used in conjunction with IPTG (Isopropyl-ß-D-thiogalactopyranoside, cat. no. 26600) which binds and inhibits the lac repressor thus inducing ß-galactosidase activity.Stock solution: 20 mg/ml in DMF. Store in aliquots at -20 °C in the dark. For detection of transformants, use in final concentration of 40 µg/ml.