IPTG (Isopropyl β-D-1-thiogalactopyranoside) induces activity of ß-galactosidase, an enzyme that promotes lactose utilization, by binding and inhibiting the lac repressor. In cloning experiments, the lacZ gene is replaced with the gene of interest and IPTG is then used to induce gene expression. IPTG is an effective inducer in the concentration range of 100μM to 1.5mM