DAPI (4′,6-diamidino-2-phenylindole) is a blue-fluorescent DNA stain that exhibits ~20-fold enhancement of fluorescence upon binding to AT regions of dsDNA. It is excited by the violet (405 nm) laser line and is commonly used as a nuclear counterstain in fluorescence microscopy, flow cytometry, and chromosome staining.
DAPI’s spectral properties make it ideal for use with green (Alexa Fluor® 488, FITC, GFP) and red (Alexa Fluor® 594, rhodamine, Texas Red®, mCherry, mKate-2) fluorophores in multicolor experiments.
Because of its high affinity for DNA, it is also frequently used for counting cells, measuring apoptosis, sorting cells based on DNA content, and as a nuclear segmentation tool in high-content imaging analysis.
DAPI is generally used to stain fixed cells since the dye is cell impermeant, although the stain will enter live cells when used at higher concentrations. For live-cell staining, Hoechst® 33342 dye is a popular cell-permeant nuclear counterstain.
Human iPSC staining using Mouse Anti Beta-Tubulin Monoclonal Antibody. Nuclei (blue) were labeled with NucBlue® Fixed Cell ReadyProbes™ Reagent (Ready-to-use liquid DAPI formulation).
Alternatives to DAPI
Life Technologies offers a number of nucleic acid stains—with various emission wavelengths—that can be used as alternatives to DAPI for imaging live cells.
Nuclear counterstaining in live cells
For live-cell staining, Hoechst® 33342 dye is a popular cell-permeant nuclear counterstain.
|BPAE cells fixed and permeabilized using the Image-iT® Fixation/Permeabilization Kit. Nuclei were stained using NucBlue® Live Cell Stain.