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beta-Galactosidase Precipitating Substrates

Detects the expression of recombinant DNA or fusion proteins containing beta-Gal.

Pierce IPTG

Thermo Scientific Pierce IPTG is isopropyl-β-D-thiogalactopyranoside for use with beta-galactosidase substrates such as X-Gal to detect expression of vectors, plasmids, or DNA fragments that contain the reporter gene.

The reagent X-Gal (5-Bromo-4-chloro-3-indolyl-β-D-galactopyranoside) is a chromogenic substrate for β-galactosidase that yields a blue precipitate, is soluble in DMF, and can be used to detect vectors, plasmids, or DNA fragments that contain the β-Galactosidase gene.

IPTG (Isopropyl-β-D-thiogalactopyranoside) may be used to maximize the expression of genes in expression vectors. When screening a lambda bacteriophage library with an antibody, the probability of success can be increased by preventing the expression of the fusion protein until the plaques are well established. By placing a nitrocellulose filter containing the inducer IPTG onto the plate and continuing growth at 37°C, the expression of the potential β-galactosidase-cDNA fusion protein can be induced after 3-4 hours of plaque growth. The nitrocellulose filter is then screened with antibodies. IPTG is also used in combination with X-Gal to detect active β-galactosidase and is practical in applications using bacteriophage M13 and Igt11 vectors.


  • X-Gal yields an intense blue precipitate to detect β-galactosidase expression
  • Can be combined with IPTG to selectively maximize the detection of β-galactosidase


  1. Maniatis, T., Fritsch, E. and Sambrook, J. (1982). Molecular Cloning: A Laboratory Manual. New York: Cold Spring Harbor Laboratory.

Related Resources:

Immunohistochemistry (IHC) technical guide

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
34060 IPTG
Formulation: Isopropyl-β-D-thiogalactopyranoside; powder or pellets (at least 99% pure)
Sufficient For: Induction of beta-galactosidase for many experiments, depending on assay format
1g MSDS for product #34060 IPTG Certificate of Analysis for product #34060 IPTG $60.00

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Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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