Fluorogenic assay of alkaline phosphatase activity based on the modulation of excited-state intramolecular proton transfer

A new fluorogenic substrate 1, which enables the fast and quantitative analysis of alkaline phosphatase activity, has been developed. Selective enzymatic hydrolysis of 1 instantly generated fluorescent compound 2 in aqueous media, which undergo an excited-state intramolecular proton transfer process, resulting in a remarkable fluorescence turn-on signal with an unusually large Stokes shift.