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Propidium Iodide (PI)

Propidium iodide (PI) is a membrane-impermeant nucleic acid intercalator. The dye is commonly used to selectively stain dead cells in a cell population and also used as a counterstain in multicolor fluorescent imaging.

Product Attributes

CAS number


Cellular localization

Nucleus & cytoplasm

Assay type/options

DNA content/cell cycle (flow cytometry), No-wash staining, Real-time imaging

Cell permeability

Membrane impermeant

Apoptosis/viability marker

Dead cell stain




493/636 nm (without DNA), 535/617 nm (with DNA)

Catalog #
10 mL (1 mg/mL in Water)
2 mL (50 ug/mL in Buffer)
100 mg
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Product Description

Propidium Iodide (PI) Products

Propidium Iodide ProductsCatalog NumberUnit SizeFormat
Propidium Iodide40016100 mgOrange red solid
Propidium Iodide, 1 mg/mL in Water4001710 mLOrange/red solution
Propidium Iodide, 50 ug/ml in Buffer400482 mLOrange/red solution

Propidium iodide (PI) is a cell impermeable nucleic acid intercalating dye. Because PI is excluded from viable cells, it can be used to distinguish necrotic or late apoptotic cells with damaged plasma membranes from viable cells or early apoptotic cells with intact cell membranes. After entering cells and binding to DNA and RNA, the fluorescence of PI is enhanced 20- to 30-fold. PI can be used in flow cytometry and fluorescence microscopy. PI is also utilized as a counterstain in multicolor fluorescent imaging, but nuclear-specific staining requires digestion of cellular RNA.

We offer PI as a solid powder (catalog no. 40016) or as a solution in either 1 mg/mL water (catalog no. 40017) or 50 ug/mL PBS (catalog no. 40048).

PI is dead cell specific in all cell types, including mammalian cells, bacteria and yeast. See our Cellular Stains Table for more information on how our dyes stain various organisms.

Product Features:

  • λExEm (DNA-bound) = 535/617 nm
  • λExEm (no DNA) = 493/636 nm
  • Store at 4°C and protect from light, especially in solution
  • C27H34I2N4
  • MW: 668.4

We also provide an apoptosis kit with PI and CF®488A fluorescently labeled Annexin V.

For PI alternatives for dead-cell staining, see our Ethidium homodimer III and 7-AAD products as well as our Live-or-Dye™ Fixable Viability Staining Kits.




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