Oxazole Yellow

Oxazole Yellow is a high-affinity, green-fluorescent stain for monomeric carbocyanine nucleic acids that is cell-impermeant. In the absence of nucleic acids, it is basically non-fluorescent, but when bound to them, it exhibits excitation/emission maxima at 491 and 506 nm. Apoptotic cells can also be recognized using oxazole yellow. Early apoptotic cells become impermeable to propidium iodide while being permeable to Oxazole Yellow.