Standard curve of 4-methylumbelliferone (4-MU) fluorescence.

Fluorescence intensity was measured using a Synergy 2 multimode microplate reader at excitation and emission wavelengths of 360 nm and 460 nm, respectively. Relative fluorescence units (RFU) obtained at low 4-MU concentrations (0–2.0 µM) are shown in the insert. Each data point represents the mean ± standard deviation (SD) of 10 independent measurements.