DAF-FM diacetate is a sensitive cell-permeable fluorescent probe important reagent for quantification of low concentrations of nitric oxide in solution. More photo-stable and less pH sensitive than DAF-2.This compound is essentially nonfluorescent until it reacts with NO to form a fluorescent benzotriazole. DAF-FM diacetate permeates well into living cells and is rapidly transformed into water-soluble DAF-FM by cytosolic esterases. With excitation/emission maxima of 495/515 nm, DAF-FM can be detected using any instrument suitable for detecting fluorescein.