β-galactosidase, encoded by the lacZ gene in E. coli, is widely used as a reporter enzyme to study gene expression, protein-protein interaction and normalization of transfection efficiency in mammalian cells. The SensoLyteŽ MUG β-Galactosidase Assay Kit provides a highly sensitive fluorogenic substrate for detection of β-galactosidase activity in tranfected cells. In the presence of β-galactosidase, the colorless 4-methylumbelliferyl β-D-galactopyranoside (MUG) substrate is hydrolyzed into a product that has bright blue fluorescence. Fluorescence can then be detected at Ex/Em = 360/460 nm. The kit contains: MUG β-galactosidase substrate, fluorescence reference standard, β-galactosidase standard, reaction buffer, stop buffer and optimized assay protocol. Assays are performed in a convenient 96-well format.