Propidium Iodide

Propidium iodide (PI) is a red-fluorescent dye widely used for staining and identifying dead cell populations in flow cytometry and fluorescence microscopy.

This product is offered as a 1 mg / mL aqueous solution.

PI is a membrane-impermeant dye that selectively binds to DNA by intercalating between nucleic acid bases with minimal sequence specificity. While viable cells with intact membranes exclude PI, it penetrates and stains cells with compromised membranes, such as those undergoing apoptosis or necrosis. PI is optimally excited at 535 nm and emits bright red fluorescence at a maximum wavelength of 617 nm, making it well-suited for detection via flow cytometry or fluorescence microscopy. For multiparametric analysis, PI can be used in combination with other fluorescent markers, such as calcein AM for live/dead cell discrimination or Annexin V FITC to differentiate between apoptotic and necrotic cells.

Due to its inability to penetrate intact cell membranes, PI selectively enters cells with compromised membranes, such as apoptotic or necrotic cells, and intercalates between the base pairs of double-stranded DNA and RNA. This intercalation significantly enhances its red fluorescence, with excitation and emission maxima at approximately 535 nm and 617 nm, respectively. PI is frequently employed in flow cytometry and fluorescence microscopy to discriminate live and dead cell populations and to quantify DNA content for cell cycle phase distribution. In apoptosis assays, PI is often used in conjunction with Annexin V to distinguish between apoptotic and necrotic cells, with Annexin V-positive/PI-negative cells indicating early apoptosis and Annexin V-positive/PI-positive cells indicating late apoptosis or necrosis. Given its potential mutagenicity, proper handling with personal protective equipment is essential.