X-Gal; 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside




The chemical name of X-Gal is X-Gal is 5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside, which is a chromogenic substrate for β-galactosidase and produces an insoluble blue color precipitate by cleaving X-Gal. The insoluble blue color precipitate can easily be detected visually over background. X-Gal is commonly used in molecular biology cloning application to detect the activity of β-galactosidase and in conjunction with IPTG for blue-white bacterial colony screening. It is also 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 and the 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.


Major Applications:

  • X-Gal is used in immune-histochemistry applications.
  • It is also the substrate of choice for blue-white selection of recombinant bacterial colonies with the lac+ genotype.

CAS No.:                     7240-90-6

Molecular weight:        408.63 g/mol

Molecular Formula:     C14H15BrClNO6

Purity:                          Greater than 99% (HPLC)

Grade:                         Molecular Biology Grade

Solubility:                    Clear (2% in DMF)

Biological Activity:       Blue color with Lambda, pUC, and M13

Storage/Handling:       Store at -20°C. Protected from Light.

PubChem Chemical ID: 619018



Precaution and Disclaimer:

X-Gal is for RESEARCH USE ONLY and harmful if swallowed. Read the product Safety Data Sheet before use in the

research laboratory only.

Catalog No. Product Name Size Storage Condition
10346 X-Gal; 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside 100 mg Desiccated at -20°C
10346-1 X-Gal; 5-bromo-4-chloro-3-indolyl-ß-D-galactopyranoside 1 g Desiccated at -20°C

Additional information


100 mg, 1 g

Certificate of Analysis