A blue nuclear counterstain for fluorescence microscopy.

DAPI (diamidino-2-phenylindole) is a blue fluorescent probe that fluoresces brightly when it is selectively bound to the minor groove of double stranded DNA where its fluorescence is approximately 20-fold greater than in the nonbound state. This selectivity for DNA, along with cell permeability allows staining of nuclei with little background from the cytoplasm, making DAPI the classic nuclear counterstain for immunofluorescence microscopy. DAPI has greater photostability than Hoechst dyes, another common nuclear counterstain, when it is bound to double stranded DNA. DAPI has an excitation maximum at 345 nm and an emission maximum at 455 nm.

DAPI is compatible with fluorescein and rhodamine dyes, as well as with DyLight* and Alexa* Fluors, for nuclear counterstaining of DNA in fluorescence imaging. Stock solutions of DAPI are stable in solution at -20°C when stored in the dark.

Properties of DAPI Dye:

Applications for DAPI stain:

• Assaying DNA in solution (ref.4)
• Diagnosing mycoplasmal infection of cell cultures (ref.5)
• Measuring nuclear content and sorting chromosomes in flow cytometry (ref.6)
• Assessing apoptosis (ref.7)
• Detecting nuclei and organellar DNA in immunofluorescent and in situ hybridization procedures (ref.2,8)
• Replacing ethidium bromide for staining DNA in agarose gels (ref.5,9)
• Counterstaining nuclei in histochemical methods when red-fluorescent antibodies have been used to detect specific targets (ref.8)
• Reports also indicate that DAPI will bind to polyphosphates and other polyanions (ref.10), dextran sulfate (ref.11) and SDS (ref.12).

Related Products and Resources

DyLight 405 is a newer blue fluorescent dye, tailored for various chemical and biological applications where greater photostability and fluorescence intensity, pH independence, and a narrower emission spectrum are required.

DyLight 405 Labeling Kits
DyLight 405 and eight other DyLight Reactive Fluors
Calculate dye:protein (F/P) molar ratios (Tech Tip #31)
All Fluorescent Labeling Reagents, including AMCA, FITC, and TRITC
Immunohistochemistry Reagents, including ABC and DAB staining kits
Thermo Scientific Cellomics* High-Content Screening (HCS) Reagents

References

1. Morikawa, K. and Yanagida, J. (1981). Visualization of individual DNA molecules in solution by light microscopy: DAPI staining method. J. Biochem. (Tokyo) 89:693-6.
2. 2. Lawrence, M.E. and Possingham, J.V. (1986). Direct measurement of femtogram amounts of DNA in cells and chloroplasts by quantitative microspectrofluorometry. J. Histochem. Cytochem. 34:761-8.
3. Kubista, M., et al. (1987). Characterization of interaction between DNA and 4', 6-diamidino-2-phenylindole by optical spectroscopy. Biochemistry 26:4545-53.
4. Brunk, C.F., et al. (1979). Assay for nanogram quantities of DNA in cellular homogenates. Anal. Biochem. 92:497-500.
5. Russell, W.C., et al. (1975). A simple cytochemical technique for demonstration of DNA in cells infected with mycoplasmas and viruses. Nature 253:461-2.
6. Hammarton, T.C., et al. (2003). Stage-specific differences in cell cycle control in Trypanosoma brucei revealed by RNA interference of a mitotic cyclin. J. Biol. Chem. 278(25):22877-86.
7. Lai, J., et al. (2003). Loss of HSulf-1 up-regulates heparin-binding growth factor signaling in cancer. J. Biol. Chem. 278(25):23107-17.
8. Soto, P., et al. (2003). SMAD2 and SMAD7 Involvement in the post-translational regulation of Muc4 via the transforming growth factor-b and interferon-g pathways in rat mammary epithelial cells. J. Biol. Chem. 278(22):20338-44.
9. Nairn, R.S., et al. (1982). Comparison of ethidium bromide and 4', 6'-diamidino-2-phenylindole as quantitative fluorescent stains for DNA in agarose gels. J. Biochem. Biophys. Meth. 6:95-103.
10. Tijssen, J.P.F., et al. (1982). Localization of polyphosphates in Saccharomyces fragilis, as revealed by 4', 6-diamidino-2-phenylindole fluorescence. Biochem. Biophys. Acta 721:394-8.
11. Allan, R.A. and Miller, J.J. (1980). Influence of S-adenosylmethionine on 4', 6-diamidino-2-phenylindole dihydrochloride (DAPI)-induced fluorescence of polyphosphate in the yeast vacuole. Can. J. Micro. 26:912-20.
12. Kapuscinski, J. and Skoczylas, B. (1978). Fluorescent complexes of DNA with DAPI (4',6-diamidine-2-phenyl indole dihydrochloride) or DCI (4',6- dicarboxyamide-2-phenyl indole). Nucl. Acids Res. 5:3775-99.

Thermo Scientific Pierce Fluorescent Dyes are available in bulk quantities and prices.

Ordering Information	Certificate of Analysis   Product Instructions   MSDS
Buy Product # Description Pkg. Size Files Price Add 46190 4',6-Diamidino-2-phenylindole, dihydrochloride (DAPI) 10 mg $128.00