- Blue/white colony screening
- Expression of cloned genes that are under control of the lac promoter
IPTG (isopropyl-beta-D-thiogalactopyranoside) is a highly stable synthetic analogue of lactose. It inactivates the lac repressor and induces synthesis of beta-galactosidase, an enzyme that
promotes lactose utilization. The IPTG is used to induce the expression of cloned genes which are under control of the lac operon. It is used in conjunction with X-Gal to determine the lac
phenotype in blue/white colony screening.
- Greater than 99.8 % purity confirmed by HPLC
- Functionally tested in blue/white colony screening
Preparation of stock solution:
Dissolve IPTG in water to a final concentration of 200 mg/ml. Sterilize solution using a 0.2 μm filter, dispense in aliquots, and store at –20°C. The sterilized solution is usually stable for
several months when stored at –20°C.
IPTG should be used at a final concentration of 250–350 μg/ml in culture plates, top agar, or liquid culture. Alternatively, an appropriate amount of IPTG can be spread onto the surface of an
agar plate and allowed to dry before inoculating with bacterial culture.
Most papers recommend using between 0.1 mM – 1.0 mM IPTG for expression.
To make it clear at the beginning IPTG titration with ranges between 0.01mM – 1.0mM and compare using SDS-PAGE to determine the needed concentration. Note: higher concentrations of IPTG can cause
IPTG can be dissolved in sterile water.
To make fresh 100mM IPTG stock solution:
Weigh 0.238 g of IPTG
Add 10 ml sterile H2O. Dissolve completely.
Prewet a 0.22 µm syringe filter by drawing through 5-10 ml of sterile H2O and discard water.
Sterilize IPTG Stock through the prepared 0.22 µm syringe filter.
Store in 1 ml aliquots at -20°C for up to 1 year.
How do you store IPTG?
Store powder IPTG desiccated at -20°C. Protect from light. For IPTG stock solution, store in 1 ml aliquots at -20°C for up to 1 year.