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. 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.

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.

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.

When S-Gal^® is cleaved by ß-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.

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

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.

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