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DAPI
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<h2 id="history">History</h2> <p>DAPI was first synthesised in 1971 in the laboratory of Otto Dann as part of a search for drugs to treat <a href="/facts/Trypanosomiasis/nqcKaxpF">trypanosomiasis</a>. Although it was unsuccessful as a drug, further investigation indicated it bound strongly to DNA and became more fluorescent when bound. This led to its use in identifying <a href="/facts/Mitochondria/ErHqrdJ1">mitochondrial</a> DNA in <a href="/facts/Ultracentrifugation/h2EyfDk2">ultracentrifugation</a> in 1975, the first recorded use of DAPI as a fluorescent DNA stain.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> </p><p>Strong fluorescence when bound to DNA led to the rapid adoption of DAPI for fluorescent staining of DNA for <a href="/facts/Fluorescence_microscopy/eMwIdrRR">fluorescence microscopy</a>. Its use for detecting DNA in <a href="/facts/Plant/X5BMDMvS">plant</a>, <a href="/facts/Metazoa/4b8J33nd">metazoa</a> and <a href="/facts/Bacteria/wC8xSCsU">bacteria</a> cells and <a href="/facts/Virus/mf88Bcbl">virus</a> particles was demonstrated in the late 1970s, and quantitative staining of DNA inside cells was demonstrated in 1977. Use of DAPI as a DNA stain for <a href="/facts/Flow_cytometry/M2IvPdL8">flow cytometry</a> was also demonstrated around this time.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p><p>When bound to double-stranded DNA, DAPI has an absorption maximum at a wavelength of 358 nm (<a href="/facts/Ultraviolet/kncBUqn5">ultraviolet</a>) and its emission maximum is at 461 nm (blue). Therefore, for fluorescence microscopy, DAPI is excited with ultraviolet light and is detected through a blue/cyan filter. The emission peak is fairly broad.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> DAPI will also bind to <a href="/facts/RNA/HxPeNfNj">RNA</a>, though it is not as strongly fluorescent. Its emission shifts to around 500 nm when bound to RNA.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <p>DAPI's blue emission is convenient for microscopists who wish to use multiple fluorescent stains in a single sample. There is some fluorescence overlap between DAPI and green-fluorescent molecules like <a href="/facts/Fluorescein/8E4xH5at">fluorescein</a> and <a href="/facts/Green_fluorescent_protein/6nWDMhSC">green fluorescent protein</a> (GFP) but the effect of this is small. </p><p>Outside of analytical fluorescence light microscopy DAPI is also popular for labeling of <a href="/facts/Cell_cultures/7Qhu13D9">cell cultures</a> to detect the DNA of contaminating <i><a href="/facts/Mycoplasma/G1T7m3rv">Mycoplasma</a></i> or <a href="/facts/Virus/mf88Bcbl">virus</a>. The labelled <i>Mycoplasma</i> or virus particles in the <a href="/facts/Growth_medium/97IMkpFP">growth medium</a> fluoresce once stained by DAPI making them easy to detect.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="modelling-of-absorption-and-fluorescence-properties">Modelling of absorption and fluorescence properties</h2> <p>This DNA fluorescent probe has been effectively modeled<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> using the <a href="/facts/Time-dependent_density_functional_theory/Wwk8tlmM">time-dependent density functional theory</a>, coupled with the IEF version of the <a href="/facts/Polarizable_continuum_model/mPJatxWU">polarizable continuum model</a>. This quantum-mechanical modeling has rationalized the absorption and fluorescence behavior given by minor groove binding and <a href="/facts/Intercalation_(biochemistry)/nkDu0lQr">intercalation</a> in the DNA pocket, in term of a reduced structural flexibility and polarization. </p> <h2 id="live-cells-and-toxicity">Live cells and toxicity</h2> <p>DAPI can be used for fixed cell staining. The concentration of DAPI needed for live cell staining is generally very high; it is rarely used for live cells.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> It is labeled non-toxic in its MSDS<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> and though it was not shown to have mutagenicity to <i>E. coli</i>,<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> it is labelled as a known mutagen in manufacturer information.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> As it is a small DNA binding compound, it is likely to have some <a href="/facts/Carcinogenic/soH8Y9CE">carcinogenic</a> effects and care should be taken in its handling and disposal. </p> <h2 id="alternatives">Alternatives</h2> <p>The <a href="/facts/Hoechst_stain/34HbebqD">Hoechst stains</a> are similar to DAPI in that they are also blue-fluorescent DNA stains which are compatible with both live- and fixed-cell applications, as well as visible using the same equipment filter settings as for DAPI. </p> <h2 id="see-also">See also</h2> Wikimedia Commons has media related to DAPI. <ul><li><a href="/facts/DNA_binding_ligand/HEMm9eDX">DNA binding ligand</a></li> <li><a href="/facts/Hoechst_stain/34HbebqD">Hoechst stain</a></li> <li><a href="/facts/Lexitropsin/UKlsF2aS">Lexitropsin</a></li> <li><a href="/facts/Netropsin/TCaJb4PI">Netropsin</a></li> <li><a href="/facts/Pentamidine/xz00bxxS">Pentamidine</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kapuscinski, J. (September 1995). "DAPI: a DNA-specific fluorescent probe". Biotech. Histochem. 70 (5): 220–233. doi:10.3109/10520299509108199. PMID 8580206. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Kapuscinski, J. (September 1995). "DAPI: a DNA-specific fluorescent probe". Biotech. Histochem. 70 (5): 220–233. doi:10.3109/10520299509108199. PMID 8580206. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Invitrogen, DAPI Nucleic Acid Stain Archived 2009-03-06 at the Wayback Machine. accessed 2009-12-08. <a href="http://probes.invitrogen.com/media/pis/mp01306.pdf" target="_blank">http://probes.invitrogen.com/media/pis/mp01306.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Scott Prahl, DAPI. accessed 2009-12-08. <a href="http://omlc.ogi.edu/spectra/PhotochemCAD/html/dapi(H2O).html" target="_blank">http://omlc.ogi.edu/spectra/PhotochemCAD/html/dapi(H2O).html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Kapuscinski, J (2017). "Interactions of nucleic acids with fluorescent dyes: spectral properties of condensed complexes". Journal of Histochemistry & Cytochemistry. 38 (9): 1323–1329. doi:10.1177/38.9.1696951. PMID 1696951. <a href="https://doi.org/10.1177%2F38.9.1696951" target="_blank">https://doi.org/10.1177%2F38.9.1696951</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Russell, W. C.; Newman, Carol; Williamson, D. H. (1975). "A simple cytochemical technique for demonstration of DNA in cells infected with mycoplasmas and viruses". Nature. 253 (5491): 461–462. Bibcode:1975Natur.253..461R. doi:10.1038/253461a0. PMID 46112. S2CID 25224870. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Biancardi, Alessandro; Biver, Tarita; Secco, Fernando; Mennucci, Benedetta (2013). "An investigation of the photophysical properties of minor groove bound and intercalated DAPI through quantum-mechanical and spectroscopic tools". Phys. Chem. Chem. Phys. 15 (13): 4596–603. Bibcode:2013PCCP...15.4596B. doi:10.1039/C3CP44058C. PMID 23423468. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Zink D, Sadoni N, Stelzer E (2003). "Visualizing Chromatin and Chromosomes in Living Cells. Usually for the live cells staining Hoechst Staining is used. DAPI gives a higher signal in the fixed cells compare to Hoechst Stain but in the live cells Hoechst Stain is used". Methods. 29 (1): 42–50. doi:10.1016/S1046-2023(02)00289-X. PMID 12543070. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>DAPI MATERIAL SAFETY DATA SHEET. kpl.com <a href="https://web.archive.org/web/20120305183437/http://www.kpl.com/docs/msds/710301.pdf" target="_blank">https://web.archive.org/web/20120305183437/http://www.kpl.com/docs/msds/710301.pdf</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Ohta T, Tokishita S, Yamagata H (2001). "Ethidium bromide and SYBR Green I enhance the genotoxicity of UV-irradiation and chemical mutagens in E. coli". Mutat. Res. 492 (1–2): 91–7. doi:10.1016/S1383-5718(01)00155-3. PMID 11377248. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Invitrogen, DAPI Nucleic Acid Stain Archived 2009-03-06 at the Wayback Machine. accessed 2009-12-08. <a href="http://probes.invitrogen.com/media/pis/mp01306.pdf" target="_blank">http://probes.invitrogen.com/media/pis/mp01306.pdf</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>