3,8-Diamino-5-[3-(diethylmethylammonio)propyl]-6-phenylphenanthridinium Iodide; 3,8-Diamino-5-(3-diethylaminopropyl)-6-phenylphenanthridinium Iodide Methiodide; [3-(3,8-Diamino-6-phenyl-5-phenanthridinio)propyl]diethylmethylammonium Diiodide; 3,8-Diamino-5-(diethylmethylaminopropyl)-6-phenylphenanthridinium Diiodide; Propidium Diiodide

Propidium iodide (PI) is a fluorescent dye [FW 668.41] that binds specifically to DNA. This property has led to its common use in evaluation of cell cycle, aneuploidy and apoptosis by flow cytometry. When excited by a laser light at 488 nm, PI emits a signal that can be monitored by the red wavelength detector typically reserved for phycoerythrin (usually FL2). Propidium iodide is excluded from viable cells, thus analysis of DNA content in cells requires membrane permeabilization. In evaluation of apoptosis, PI is used to distinguish necrotic cells or cells in late stages of apoptosis, which have permeabilized membranes and thus bind PI, from viable cells or cells in early apoptosis where membranes are intact and PI is excluded.