X-Gal (5-Bromo-4-chloro-3-indoxyl-beta-D-galactopyranoside)

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SKU: RC-113-XX Category:
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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-complemtation 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 for blue/white screening.
  • 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


  • CAS#: 7240-90-6
  • Molecular Formula: C14H15BrClNO6
  • Molecular Weight: 408.63 g/mol




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