Propidium iodide (PI) is a membrane-impermeant nucleic acid intercalator. The dye is commonly used to selectively stain dead cells in a mixed live-dead population and also used as a counterstain in multicolor fluorescent assays.
0.5 mL (2 mM in DMSO)
DNA & RNA dye
Nucleus & cytoplasm
Fluorescence microscopy, Flow cytometry
Dead cell stain
528/617 nm (with DNA)
Ethidium Homodimer I dye (EthD-I) is highly positively charged, it cannot cross cell membranes to stain living cells. It is useful for detecting nucleic acids in solution or for selectively staining dead cells with damaged plasma membranes in all cell types, including mammalian cells, bacteria and yeast.
High-affinity red fluorescent nucleic acid stain
Dead cell specific in all cell types, including mammalian cells, bacteria and yeast
Available as a high-purity powder or solution
Ethidium Homodimer (solid)
Ethidium Homodimer (2 mM in DMSO)
Ethidium Homodimer I is offered at high purity grade that is not available from other manufacturers. Ethidium Homodimer from other suppliers often contains a high amount (as much as 20%) of inorganic salt that lowers the weight percent purity. The dye is not base pair specific and is believed to label nucleic acid by intercalation.
Find the Right Stain for Your Application
EthD-I binds to both DNA and RNA in a sequence-independent manner and with a >30-fold fluorescence enhancement. EthD-1 is a widely used alternative to Propidium Iodide since the high affinity of EthD-I permits the use of a lower dye concentration and no-wash staining. Biotium developed Ethidium Homodimer III, as a superior alternative to EthD-I. The absorption and emission spectra are similar, but EthD-III is 45% brighter. Biotium also offers other dead-cell stains in other colors and with other beneficial properties such as Live-or-Dye NucFix™ Red which, unlike EthD-I, is a fixable dead-cell stain. See our Cellular Stains Selection Guide and Cellular Stains Table for more information. Learn more about EthD-I and other dead-cell specific stains.
Biotium also offers other live-cell specific stains in other colors and with other beneficial properties. Such as NucSpot® Live Cell Nuclear Stains, which are cell-membrane permeable DNA dyes that specifically stain nuclei in live or fixed cells. They have excellent specificity for DNA without the need for a wash step, and they have low toxicity for live cell imaging.