Oxazole Red Homodimer, also known as YOYO®-3, is a bright, high-affinity, cell-impermeant dimeric far-red nucleic acid dye (Ex/Em at 612/631 nm) . It is essentially nonfluorescent until bound to nucleic acids, making it a useful dead cell stain for microscopy or flow cytometry. 1 mM in DMSO.