X-a-Gal [5-Bromo-4-Chloro-3-indolyl-a-D-galactoside], 250 Milligrams

Chromogenic substrate for detection of a-galactosidase activity in yeast Saccharomyces cerevisiae. Used in yeast Two-Hybrid System to detect protein-protein interactions within random libraries. The enzyme a-galactosidase enabels yeast to use disaccharide melibose as a carbon source during growth or fermentation. Secretion of this enzyme in response to activation of the GAL4 gene hydrolizes X-a-GAL and causes yeast colonies to develop a blue color. This reporter system allows immediate visible results on selection plates and eliminates necessity of a second screen filter life assay.