The ONPG assay kit is ideal to quantify high expression level of beta-Gal. The levels of active beta-Gal expression can be quickly measured by its catalytic hydrolysis of ONPG (o-nitrophenyl-beta-D-galactopyranoside) substrate to a bright yellow product (Absorbance at 405-420nm).LacZ is one of the most frequently reporter gene used in transfection experiments. The LacZ encoded protein (beta-galactosidase, beta-Gal), is very stable, resistant to proteolytic degradation and easily assayed. All the necessary reagents are provided in this assay kit and offer a rapid, simple and sensitive method to quantify spectrophotometrically the enzyme expression level in LacZ transfected cells. *Convenient for all transfection assays *Suitable for cultured cells and tissues *Simple, rapid and easy-to-use *Economical *Optimized with stable buffers