V. Shah, T. Charlton, and J. Kim, Appl. Biochem. Biotechnol. 184, 1232-1246 (2018)
“…Enzyme Activity Assay. The initial rate of enzymatic hydrolysis of a substrate, ONPX2, was measured by monitoring changes in absorbance at 400 nm over time using a Varian Cary 50 UV-VIS spectrophotometer fitted with a Quantum Northwest Peltier temperature control unit…”