β-galactosidase, encoded by the lacZ gene inE. coli, is widely used as a reporter enzyme to study gene expression, protein-protein interaction and normalization of transfection efficiency in mammalian cells. The SensoLyte® FDG β-Galactosidase Assay Kit provides a sensitive fluorogenic substrate for detecting β-galactosidase activity in tranfected cells. In the presence of β-galactosidase, the colorless fluorescein di-β-D galactopyranoside (FDG) substrate is hydrolyzed into a fluorescein that can be detected at Ex/Em = 490/520 nm. The kit contains: FDG 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. Kit size: 500 assays