X-Gal

5-Bromo-4-chloro-3-indolyl beta-D-galactopyranoside is most commonly known as X-Gal. X-gal is a histochemical substrate for beta-galactosidase which cleaves X-Gal to yield an insoluble blue precipitate.

• Molecular Biology Grade

• Purity: Greater than 99% (HPLC)
• Solution: Clear (2% in DMF)
• Biological Activity: Blue colour with Lambda, pUC, and M13

X-Gal is a mainstay in molecular biology cloning applications in which it is used to detect the activity of beta-galactosidase. X-Gal is used to detect the insertion of foreign DNA into the lacZ region of a plasmid DNA. Insertion of DNA into the lacZ region results in the loss of beta-galactosidase activity. Bacteria cells that retain active beta-galactosidase will result in characteristic blue colonies. Successful disruption of the lacZα gene disrupts the α-complemtation of the beta-galactosidase gene and the precipitate does not form, resulting in white colonies.

Many other applications also use X-Gal as a substrate to detect beta-galactosidase activity. These include beta-galactosidase -antibody linked immunoassays and immunohistochemistry, coliphage detection based on beta-galactosidase induction and the detection of micrometastasis formation during tumor progession.

X-gal is commonly used in conjunction with IPTG for blue/white screening.