Propidium iodide is a commonly used dead-cell stain that emits red fluorescence when bound to DNA. Propidium iodide is also used as a counterstain in multicolor fluorescent techniques. With Propidium Iodide ReadyProbes® Reagent, we provide a room temperature-stable solution of classic DNA stain that comes in a convenient-to-use dropper bottle. Just tip and drip two drops per ml to stain your cells.

Also available: Propidium Iodide, Fluorspar grade at 12.5X concentration (13.2 μg/mL, 19.7 μM) in water with 1% DMSO.

See other Ready Probes ready-to-use imaging reagents and accessories ›

Features of Propidium Iodide ReadyProbes® Reagent:
• Ready-to-use liquid propidium iodide formulation
• Rapid staining of dead cells without wash steps
• Ready-to-use liquid formulation in convenient dropper bottle—no need to dilute, weigh, or pipette
• Stable at room temperature—keep handy at your work station or cell culture area

Classic Dead Cell Stain
Propidium iodide is a classic fluorescent dye used extensively for staining of dead cells (Figure 1). It exhibits a sufficiently large Stokes shift to allow simultaneous detection of nuclear DNA and FITC or Alexa Fluor® 488-labeled antibodies.

Packaged for Convenience
Propidium Iodide ReadyProbes® Reagent is supplied ready-to-use and can be stored right next to your flow cytometer or in your cell culture lab. A liquid formulation in an ultra-convenient dropper bottle (Figure 2) allows you to stain your cells whenever and wherever they are ready. Just add two drops per ml for optimally bright and distinct nuclear counter-staining.

Multiple Applications
Propidium iodide is membrane-impermeant and excluded from viable cells. It is therefore commonly used for identifying dead cells in a population. Its spectral properties, selectivity for dsDNA, and increased fluorescence when bound to DNA, make propidium iodide ideal for use with green (Alexa Fluor® 488, FITC, GFP) fluorophores in multicolor experiments. Because of its high affinity for DNA, it is also frequently used for counting cells, measuring apoptosis, and sorting cells based on DNA content.

Suggestions for Use
• In most cases, 2 drops/1×10⁶ cells of Propidium Iodide ReadyProbes® Reagent and an incubation time of 15 to 30 minutes will produce bright nuclear staining; however, optimization may be needed for some cell types, conditions, and applications. In such cases, simply add more or fewer drops until the optimal staining intensity is obtained.
• When bound to nucleic acids, the fluorescence excitation maximum for propidium iodide is 535 nm and the emission maximum is 617 nm. Propidium iodide can be excited with a xenon or mercury-arc lamp or with the 488 line of an argon-ion laser. Generally, propidium iodide fluorescence is detected in the FL2 channel of flow cytometers.
• As a preferred red nuclear stain in dead cell analyses using flow cytometry, Propidium Iodide ReadyProbes® Reagent is ideal for use with antibody-based applications.

See other Molecular Probes® imaging tools and reagents.