Isopropyl β-D-1-thiogalactopyranoside

Isopropyl β-D-1-thiogalactopyranoside (IPTG, also known as lad-y) is a molecular biology reagent. This compound is a molecular mimic of allolactose, a lactose metabolite that triggers transcription of the lac operon, and it is therefore used to induce protein expression where the gene is under the control of the lac operator.