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DAPI is a popular blue fluorescent DNA dye. The dye binds to the minor groove of dsDNA with approximately 20-fold fluorescence enhancement.

Product Attributes

CAS number

28718-90-3 (DAPI, Dihydrochloride), 28718-91-4 (DAPI, Dilactate)

Probe cellular localization


For live or fixed cells

For fixed cells, For live/intact cells

Detection method/readout

Fluorescence microscopy, Flow cytometry

Assay type/options

DNA content/cell cycle profiling by flow cytometry, Long term staining (24-72h), No-wash staining, Real-time imaging, Tissue staining

Cell permeability

Membrane permeant

Apoptosis/viability marker

All cell stain




358/461 nm (with DNA)

Storage Conditions

Store at 2 to 8 °C, Protect from light

Catalog #
10 mg
10 mg (Dilactate)
1 mL (10 mg/mL)
Clear selection
(Please select quantity above )

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Product Description

DAPI (4′,6-Diamidino-2-Phenylindole, dihydrochloride) is a popular blue DNA dye that is used as a nuclear counterstain in fluorescence microscopy, chromosome staining, and flow cytometry. The dye binds to the minor groove of dsDNA with approximately 20-fold fluorescence enhancement, with higher affinity for A-T rich regions.

  • Classic blue nuclear counterstain for fixed cells
  • Available as a powder or solution
  • Can be used at higher concentrations to stain live cells
  • λExEm (with DNA) = 358/461 nm
  • Store at 4°C and protect from light, especially in solution

DAPI as a dilactate powder is more water soluble than the dihydrochloride salt, and therefore a better choice for preparing stock solutions in water. If mounting media will be used, we also offer anti-fade mounting media containing DAPI, in both hardset and wetset formulations. Having trouble with your experiments? See our section on troubleshooting tips for fluorescent staining.

ProductCatalog NumberMWUnit SizeFormat
DAPI Powder
40009457.4910 mgYellow solid
DAPI Powder
40011350.2510 mgYellow solid
DAPI Solution
40043457.491 mL
(10 mg/mL in water)
Yellow solution

Find the Right Nuclear Stain for Your Application

DAPI can be used to stain mammalian cells as well as gram-positive and gram-negative bacteria. In yeast, the staining is weak and not nuclear. DAPI is less membrane permeant than Hoechst, and is typically used to stain fixed cells. On the other hand, Hoechst dyes are membrane-permeant and more often used for live or fixed cell staining and cell cycle analysis. While Hoechst and DAPI show less cytotoxicity than intercalating DNA dyes, they bind DNA in living cells and are potentially hazardous. DAPI and Hoechst undergo photoconversion by UV excitation to form green fluorescent dyes, which can lead to artifacts in multi-color imaging. See our Tech Tip Avoiding Artifacts from UV Photoconversion of DAPI and Hoechst for more information.

Biotium offers other nuclear stains with beneficial properties such as other colors and dead-cell specific stains. See our Cellular Stains Selection Guide and Cellular Stains Table for more information. Learn more about DAPI and our novel nuclear stains.

DAPI, dilactate
DAPI, dilactate
DAPI, hydrochloride
DAPI, hydrochloride


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