For blue/white colony screening, we recommend using X-Gal / IPTG Solution at a 500-1000X concentration.
Blue/white colony screening
X-Gal / IPTG Solution is a ready-to-use solution of 40mg/ml X-Gal (5-bromo-4-chloro-3-indolyl ß-D-galactopyranoside) and 24mg/ml IPTG (Isopropyl b-D-thiogalactopyranoside) in a non-hazardous and non-toxic solvent (N-methylpyrrolidon). The X-Gal / IPTG Solution saves time and money, since no extra sterilization is necessary, and it can be used directly from the freezer. The solution provides optimal blue/white colony screening and is compatible with all commonly used lacZ expression systems in bacteria, yeast and mammals.