S-Gal^® sodium salt

S-Gal^® (sodium salt) is an autoclavable, water-soluble, chromogenic substrate for β-galactosidase, used to determine the presence or absence of a cloned DNA insert in bacteria growing on agar plates. S-gal^® is designed to replace X-Gal in blue-white selection of recombinant bacterial colonies with the lac+ phenotype.

S-Gal, sodium salt is a patented water-soluble, autoclavable chromogenic substrate for β-galactosidase that is designed to replace X-Gal in blue-white selection of recombinant bacterial colonies with the lac⁺ phenotype.

When S-Gal^® is cleaved by β-galactosidase, the resulting product will chelate ferric ion to create a black, insoluble precipitate. Lac+ colonies grown in the presence of S-Gal^® and ferric ion turn an intense black color, allowing for easy differentiation between lac+ and lac- colonies.

When S-Gal is cleaved by β-galactosidase, the resulting product will chelate ferric ion to create a black, insoluble precipitate. Lac⁺ colonies grown in the presence of S-Gal and ferric ion turn an intense black color, allowing for easy differentiation between lac⁺ and lac^- colonies. S-Gal, Sodium salt is water soluble, eliminating the need for solvents such as dimethyl formamide. S-Gal is also autoclavable and can be added to your medium of choice prior to autoclaving. S-Gal is not light sensitive and does not require any protection from light sources.

Add to agar media pre-autoclaving at a recommended concentration of 300 mg S-Gal/L of media, along with 500 mg/L Ferric Ammonium Citrate (F5879). Stock solutions of S-Gal can be made by dissolving at 50 mg/mL in deionized water, sterile-filtering and storing at -20 °C.

Stock solutions of S-Gal^® (sodium salt) can be made by dissolving 50mg/ml in water, dimethyl formamide (DMF) or DMSO. Filter sterilize and store at -20C. Add S-gal^® (300 mg/L from stock solution or powder) and Ferric Ammonium Citrate (500mg/L) to agar media prior to autoclaving.

Ferric Ammonium Citrate (F5879), LB Agar (L2897), IPTG (Isopropyl β-D-thiogalactopyranoside, I6758), Ampicillin (A2804), Kanamycin (K0879), Chloramphenicol (C7795), Tetracycline (T8032)

More water soluble version, soluble >50 mg/mL.

The ferric or Fe³⁺ ion is required for color development and must be added to any S-Gal^®
formulation. A medium prepared with S-Gal^® is moderately dark due to the presence of ferric ammonium citrate. This darker background often provides enhanced contrast for automated colony counting or isolation.

S-GAL is a registered trademark of Merck KGaA, Darmstadt, Germany

For black color development to occur, ferric ion must be present. Although we recommend ferric ammonium citrate (500 mg/L of media), other ferric compounds can be used to provide this requirement, depending upon your particular system.