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.

Product Specifications:
X-Gal;
5-Bromo-4-chloro-3-indoxyl-beta-D-galactopyranoside

MOLECULAR BIOLOGY GRADE

Formula: C₁₄H₁₅BrClNO₆

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