propidium iodide
{{chembox
| verifiedrevid = 464216583
| ImageFile=Propidium iodide.svg
| ImageSize=200px
| IUPACName=
| OtherNames=
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 94732
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 345124
| InChI = 1/C27H33N4.2HI/c1-4-31(3,5-2)17-9-16-30-26-19-22(29)13-15-24(26)23-14-12-21(28)18-25(23)27(30)20-10-7-6-8-11-20;;/h6-8,10-15,18-19,29H,4-5,9,16-17,28H2,1-3H3;2*1H/q+1;;/p-1
| InChIKey = XJMOSONTPMZWPB-REWHXWOFAB
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C27H33N4.2HI/c1-4-31(3,5-2)17-9-16-30-26-19-22(29)13-15-24(26)23-14-12-21(28)18-25(23)27(30)20-10-7-6-8-11-20;;/h6-8,10-15,18-19,29H,4-5,9,16-17,28H2,1-3H3;2*1H/q+1;;/p-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = XJMOSONTPMZWPB-UHFFFAOYSA-M
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo=25535-16-4
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = TP416O228T
| PubChem=104981
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 51240
| SMILES = CC[N+](C)(CC)CCC[n+]1c2cc(N)ccc2c3ccc(N)cc3c1c4ccccc4.[I-].[I-]
}}
|Section2={{Chembox Properties
| Formula=C27H34I2N4
| MolarMass=668.3946
| Appearance=
| Density=
| MeltingPt=
| BoilingPt=
| Solubility=
}}
|Section3={{Chembox Hazards
| MainHazards=
| FlashPt=
| AutoignitionPt =
}}
}}
Propidium iodide (or PI) is a fluorescent intercalating agent that can be used to stain cells and nucleic acids. PI binds to DNA by intercalating between the bases with little or no sequence preference. When in an aqueous solution, PI has a fluorescent excitation maximum of 493 nm (blue-green), and an emission maximum of 636 nm (red). After binding DNA, the quantum yield of PI is enhanced 20-30 fold, and the excitation/emission maximum of PI is shifted to 535 nm (green) / 617 nm (orange-red).{{cite web |url=https://www.thermofisher.com/us/en/home/life-science/cell-analysis/fluorophores/propidium-iodide.html |title=Propidium Iodide |author= |date=2019-11-14 |publisher=Thermo Fisher Scientific |access-date=2019-11-14 }} Propidium iodide is used as a DNA stain in flow cytometry to evaluate cell viability or DNA content in cell cycle analysis, {{cite web|url=http://www.biolegend.com/propidium-iodide-solution-2651.html|title=Propidium Iodide Solution - BioLegend|access-date=10 January 2015|archive-url=https://web.archive.org/web/20150210095844/http://www.biolegend.com/propidium-iodide-solution-2651.html|archive-date=10 February 2015|url-status=dead}} or in microscopy to visualize the nucleus and other DNA-containing organelles. Propidium Iodide is not membrane-permeable, making it useful to differentiate necrotic, apoptotic and healthy cells based on membrane integrity.{{cite journal |author=Lecoeur H |title=Nuclear apoptosis detection by flow cytometry: influence of endogenous endonucleases |journal=Exp. Cell Res. |volume=277 |issue=1 |pages=1–14 |year=2002 |pmid=12061813 |doi=10.1006/excr.2002.5537}}{{cite web|title=Propidium Iodide|url=https://www.thermofisher.com/order/catalog/product/P1304MP|publisher=ThermoFisher}} PI also binds to RNA, necessitating treatment with nucleases to distinguish between RNA and DNA staining.{{cite journal|vauthors=Suzuki T, Fujikura K, Higashiyama T, Takata K|date=1 January 1997|title=DNA staining for fluorescence and laser confocal microscopy|journal=J. Histochem. Cytochem.|volume=45|issue=1|pages=49–53|doi=10.1177/002215549704500107|pmid=9010468|doi-access=free}} PI is widely used in fluorescence staining and visualization of the plant cell wall.{{cite journal|last1=Bidhendi|first1=AJ|last2=Chebli|first2=Y|last3=Geitmann|first3=A|title=Fluorescence Visualization of Cellulose and Pectin in the Primary Plant Cell Wall|journal=Journal of Microscopy|volume=278 |issue=3 |pages=164–181|date=May 2020|doi=10.1111/jmi.12895|pmid=32270489|s2cid=215619998}}