4-MUG

4-Methylumbelliferyl-β-D-galactoside (MUG) is a fluorogenic substrate for β-galactosidase, releasing fluorescent 4-methylumbelliferone (4-MU) upon enzymatic cleavage. It is widely used to detect and quantify β-gal activity in both in vitro assays and in vivo applications within bacterial, yeast, and mammalian cell research. The fluorescence of the 4-MU product is pH-dependent, with excitation maxima shifting from 330 to 385 nm across a pH range of 4.6 to 10.4.