IPTG (isopropylthio-beta-D-thiogalactopyranoside) is an inducer of beta-galactosidase production in bacteria

IPTG is used together with the chromogenic substates X-gal or Bluo-Gal to determine lac gene expression in recombinant methods. IPTG is a chemical analog of galactose which cannot be cleaved by the enzyme ß-galactosidase. Therefore, it can serve as an inducer for activity of the E. coli lac operon by binding and inactivating the lac repressor. A stock solution, 0.1M, is prepared by dissolving IPTG in water with subsequent sterile filtration of the solution. The final concentration of IPTG in indicator plates-added after autoclaving should be approximately 0.2 mM/L. Store Frozen. Molecular weight: 238.21. White, free-flowing powder appearance. Melting point, 118°C.