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DAPI is a popular nuclear and chromosome counterstain, showing a distinct banding pattern in chromosomes. DAPI emits blue fluorescence upon binding to the minor groove of dsDNA with a ~20-fold fluorescence enhancement. DAPI is provided as a 5 mg solid (C001) and a 5 mg/mL aqueous solution (C002).

Excitation/Emission: 358/461 nm
Shipping Condition: Ambient
Storage Conditions: 2-8ºC, protect from light
Molecular Formula: C16H17Cl2N5
Molecular Weight: 350.25
CAS Number: 28718-90-3


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Buy Cat.No. Product name Ex/Em (nm) Size Price

DAPI 358/461 5 mg
1 ml



Protocol (PDF): C001 C002
COA (PDF):  COA-C001 COA-C002


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Frequently Asked Questions (FAQs)

Is DAPI a good live-cell nuclear label?
DAPI is considered a semi-permeant/impermeant nucleic acid stain. Staining of nucleic is dependent upon the cell line in its performance. Some cell lines will label with DAPI, others not at all, and others label non-uniformly. Instead, we recommend using either Hoechst 33342 or Hoechst 33258, which have the same wavelength and binding mode as DAPI (at the A-T minor groove) but are readily cell-permeant.

My DAPI labeled samples have a strong blue background signal immediately after mounting. What can I do to fix this?
Some mounting medias can have strong blue autofluorescence. If you are seeing a high blue background, it could be coming from the mountant. Try labeling the sample and view it before (using a wet mount in buffer) and after mounting to determine if the background signal is coming from the mounting media or the sample itself.

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