Ethidium monoazide bromide (EMA) is a fluorescent nucleic acid stain with a photoaffinity label. The dye, after photolysis, binds covalently to nucleic acids.The dye has been used to footprint drug binding sites on DNA, to modify plasmid DNA, and for labeling yeast cells for leukocyte phagocytosis assays. A particularly useful application of the dye is to label dead cells in a mixed population of live and dead cells. Because EMA