Flubida-2 has been used to detect pH at a specific site in a cell such as cell organelles by directing the probe to where avidin fusion proteins are located. The probe is a conjugate of biotin and fluorescein diacetate, which is nonfluorescent until the probe has entered the cells and hydrolyzed by endoesterases.Flubida-2 is membrane-permeable and thus can be delivered into cells via simple incubation with the probe in a buffer.
