CAY10730 is a turn-on fluorescent probe for the detection of nitroreductase activity, a marker of hypoxia. In the presence of nitroreductase, CAY10730 is transformed into a highly fluorescent molecule that displays excitation/emission maxima of 454/520 nm, respectively. It is selective for nitroreductase over a variety of bioanalytes, including glutathione, ascorbic acid, and reactive oxygen species such as H2O2. CAY10730 (1 µM) has been used to detect hypoxia in A549 human lung carcinoma cells.