X_Products

5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside is most commonly known as X-Gal. X-gal is a histochemical substrate for β-galactosidase which cleaves X-Gal to yield an insoluble blue precipitate.

X-Gal is a mainstay in molecular biology cloning applications in which it is used to detect the activity of β-galactosidase. X-Gal is used to detect the insertion of foreign DNA into the lacZ region of a plasmid DNA. Insertion of DNA into the lacZ region results in the loss of β-galactosidase activity. Bacteria cells that retain active β-galactosidase will result in characteristic blue colonies. Successful disruption of the lacZα gene disrupts the α-complementation of the β-galactosidase gene and the precipitate does not form, resulting in white colonies.

Many other applications also use X-Gal as a substrate to detect β-galactosidase activity. These include β-galactosidase -antibody linked immunoassays and immunohistochemistry, coliphage detection based on β-galactosidase induction and the detection of micrometastasis formation during tumor progession.

X-Gluc is a chromogenic substrate for beta-glucuronidase (GUS) which is encoded by the gusA (uid A) gene, a widely used reporter gene. Glucuronidase cleaves X-Gluc to produce colorless glucuronic acid and an intense blue precipitate. X-Gluc is often used in GUS staining of plant cells and tissue and in infections caused by E. coli.

X-pal is an off white to light brownish powder that is used as a chromogenic substrate for carboxylesterase. X-pal yields a blue precipitate when cleaved.

X-Sulfate K is a slightly off-white to faint-yellowish powder that is used as a chromogenic substrate for aryl-sulfatase. X-Sulfate K yields a blue precipitate when cleaved.

X-α-Gal is a chromogenic substrate for α-galactosidase, yielding a blue precipitate. X-α-Gal is used for detecting two-hybrid interactions directly on the culture media. This substrate eliminates the need for β-galactosidase liquid and filter-lift assays in two-hybrid analysis.
Used for species differentiation within the family Enterobacteriaceae and differentiation of Bifidobacteria species from Lactobacilli species.

α-L-Fucosidases are carbohydrate-processing enzymes belonging to the exoglycosidase family of glycoside hydrolases. These enzymes break down glycosidic bonds of sugars at the terminal ends. Fucose –containing glycolipids and glycoproteins can accumulate in different tissues when α-L-Fucosidase is inactive.

X-α-L-fucopyranoside is used as a chromogenic substrate for α-L-Fucosidase, producing a blue precipitate.

XCL1 is a chemokine lacking the first and third conserved cysteine residues usually found in chemokines. It is expressed in thymic and peripheral blood CD8+ T-cells and in natural killer cells. Highest levels of expression are seen in spleen, thymus, small intestine, and peripheral blood leukocytes. XCL1 is chemotactic for natural killer cells and CD4+ and CD8+ T-cells. It assumes two distinct conformations, one of which has been shown to inhibit HIV-1 isolates. XCL1 is a ligand for XCR1 as well as the virus-encoded viroreceptor M3.

GoldBio growth factors are manufactured for RESEARCH USE ONLY and cannot be sold for human consumption!

XTT sodium salt is used in the XTT colormetric assay and assists in identifying metabolic activity within cells. In the XTT assay, the metabolic activity of cells reduces XTT sodium salt to an orange color formazan dye by dehydrogenase enzymes. Dye conversion will only occur in viable cells.

Xylenol Blue is a useful alternative to thymol blue developed in the 1920s. Xylenol Blue can be used at half the concentration that thymol blue requires. It is functional at the same two pH ranges, acidic (pH 1-3), which transitions from red to yellow, and basic (pH 8-10), which transitions from yellow to blue. Xylenol Blue may be substituted for any experiment that requires thymol blue.

Xylitol is a sugar alcohol typically used as a sweetener. In humans it is typically seen to cause remineralization of teeth along with the reduction in cavities. It also is absorbed less than typical sucrose and carries a lower calorie content. Xylitol inhibits the growth of Streptococcus pneumonia and attachment of Haemophilus influenza on nasopharyngeal cells.