The cell-impermeant viability indicator ethdium homodimer-2 (EthD-2) is a high-affinity nucleic acid stain that is weakly fluorescent until bound to DNA and emits red fluorescence (excitation/emission maxima ∼535/624).
Note: A protocol is not included with this classic reagent as they are readily available in the literature. The reagent is provided already dissolved at 1 mM in DMSO. A typical protocol for staining dead cells is to prepare a working solution at 0.1 to 10 μM in a physiological buffer and incubate with cells for 30-45 minutes at room temperature before analyzing on a fluorescent microscope, flow cytometer, or plate reader.