Fluorogenic substrate used to measure sensitively enzymatic neuraminidase activity in fluorometric assays in mammalian and viral sources. Neuraminidase is catalyzed by the hydrolysation to form N-acetylneuraminic acid and the blue fluorescent soluble compound 4-Methylumbelliferone, which can be detected fluorometrically. Spectral data: lambdaex 315 nm| lambdaem 374 nm (pH.7.0) or lambdaex 365 nm| lambdaem 445 nm (after cleavage by neuraminidase). Used for fluorescent staining of sialidases in PAGE.