Propidium Iodide (ultra pure)

Propidium iodide (PI) belongs to the same chemical class as ethidium bromide. As with ethidium bromide, its fluorescence is enhanced 20-30-fold upon binding to nucleic acids. The fluorescence excitation maximum is red-shifted 30-40 nm and the fluorescence emission maximum blueshifted ~15 nm. PI also binds to RNA as does DAPI and acridine orange. PI is membrane impermeant and is commonly used for identifying dead cells in a mixed population of cells and as a counter-stain in multicolor fluorescent techniques.