Description_x000D_ General description_x000D_ 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._x000D_ Packaging_x000D_ 1, 5 g in poly bottle_x000D_ 100 mg in poly bottle_x000D_ Application_x000D_ 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._x000D_ Features and Benefits_x000D_ • More intense color contrast than X-gal_x000D_ • Water-soluble and autoclavable for easiest use_x000D_ • Excellent for use in automated colony counters_x000D_ • No need to make stock solutions_x000D_ 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._x000D_ Other Notes_x000D_ More water soluble version, soluble >50 mg/mL._x000D_ The ferric or Fe3+ ion is required for color development and must be added to any S-Gal®_x000D_ 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._x000D_ Caution_x000D_ 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._x000D_ Principle_x000D_ 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._x000D_ Linkage_x000D_ Ferric Ammonium Citrate (F5879), LB Agar (L2897), IPTG (Isopropyl β-D-thiogalactopyranoside, I6758), Ampicillin (A2804), Kanamycin (K0879), Chloramphenicol (C7795), Tetracycline (T8032)_x000D_ Reconstitution_x000D_ 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._x000D_ 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._x000D_ Legal Information_x000D_ S-GAL is a registered trademark of Sigma-Aldrich Co. LLC