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5-Bromo-4-chloro-3-indolyl-β-D-galactoside (X-Gal)

research grade

(X-Gal)
C₁₄H₁₅BrClNO₆ • M_r 408.6 • CAS [7240-90-6]

X-gal is a well known histochemical substrate used to detect the β-galactosidase enzyme (1, 2, 3, 4, 9, 10). Identification of lac^f-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-β-D-thiogalactopyranoside, cat. no. 26600) which binds and inhibits the lac repressor thus inducing β-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.

Assay (HPLC)

min. 99 %

References:

Maloy, S.R. (1990) Experimental Techniques in Bacterial Genetics, Jones and Bartlett (eds.), Boston, MA
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. Davies et al. (1980) Advanced Bacterial Genetics, Cold Spring Harbor, N.Y.