Thermo Scientific Pierce IPTG is isopropyl-ß-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-ß-D-galactopyranoside) is a chromogenic substrate for beta-galactosidase that yields a blue precipitate, is soluble in DMF, and can be used to detect vectors, plasmids, or DNA fragments that contain the ß-Galactosidase gene.
IPTG (Isopropyl-ß-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 ß-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 ß-galactosidase and is practical in applications using bacteriophage M13 and Igt11 vectors.
- X-Gal yields an intense blue precipitate to detect beta-galactosidase expression
- Can be combined with IPTG to selectively maximize the detection of beta-galactosidase
1. Maniatis, T., Fritsch, E. and Sambrook, J. (1982). Molecular Cloning: A Laboratory Manual.
New York: Cold Spring Harbor Laboratory.
Review of Immunohistochemistry