5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside is most commonly known as X-Gal. X-gal is a histochemical substrate for β-galactosidase which cleaves X-Gal to yield an insoluble blue precipitate.
X-Gal is a mainstay in molecular biology cloning applications in which it is used to detect the activity of β-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 β-galactosidase activity. Bacteria cells that retain active β-galactosidase will result in characteristic blue colonies. Successful disruption of the lacZα gene disrupts the α-complementation of the β-galactosidase gene and the precipitate does not form, resulting in white colonies.
Many other applications also use X-Gal as a substrate to detect β-galactosidase activity. These include β-galactosidase -antibody linked immunoassays and immunohistochemistry, coliphage detection based on β-galactosidase induction and the detection of micrometastasis formation during tumor progession.
X-gal is commonly used in conjunction with IPTG (GoldBio #I2481) for blue-white screening.
MOLECULAR BIOLOGY GRADE
MW: 408.63 g/mol
Purity: Greater than 99% (HPLC)
Solution: Clear (2% in DMF)
Biological Activity: Blue color with Lambda, pUC, and M13
Storage/Handling: Store at -20°C. Protect from Light.
PubChem Chemical ID: 619018
|Grade||MOLECULAR BIOLOGY GRADE|
|Storage/Handling||Store at -20°C. Protect from light.|
Protocol for adding X-Gal and IPTG to agar or plates for Blue/White screening method of bacterial transformation
Procedure for noncovalent protein internalization using β-Gal and X-Gal, by Wang et al. (2006).