Fluorescence Quenching Effect of a Highly Active Nitroxyl Radical on 7-amino-4-methylcoumarin and Glutathione Sensing.

Nitroxyl radical compounds, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), are stable radical compounds with a variety of unique characteristics, including fluorescence quenching. In this study, we investigated the fluorescence quenching effect of nortropine N-oxyl (NNO), which is a highly active nitroxyl radical that is more active than TEMPO in oxidation catalysis. The fluorescence intensity of 7-amino-4-methylcoumarin (AMC) was quenched by NNO and TEMPO to 5% and 95% of the initial fluorescence intensity, respectively, indicating highly efficient quenching by NNO.