DAPI

Principle

The fluorescent dye DAPI binds selectively to DNA and forms strongly fluorescent DNA-DAPI complexes with high specificity. DAPI, once added to tissue culture cells, is rapidly taken up into cellular DNA, yielding highly fluorescent nuclei and no detectable cytoplasmic fluorescence. When the cells are contaminated with Mycoplasmas, characteristic discrete fluorescent foci are readily detected over the cytoplasm and sometimes in intercellular spaces.

Preparation Note

Working solution: Solubility: 25 mg/ml in water


Preparation of stock solution

Dissolve in double-dist. water to a final concentration of 1 to 5 mg/ml.
Note: Do not use any buffers.


Preparation of working solution

Dilute the stock solution with methanol to a final concentration of 1 μg/ml. The working solution is stable at 2 to 8 °C for about 6 months.
Storage conditions (working solution): Stock solution (1 to 5 mg/ml) at -15 to -25 °C for 12 months.
Working solution (1μg/ml) at 2 to 8 °C for about 6 months.

Quality

Purity: >90% (from N)

Reconstitution

In 2 to 10 ml double-dist. water; 1 to 5 mg/ml final concentration.
Note: Prepare aliquots and store at -15 to -25 °C.

Application

DAPI is a fluorescent dye that binds selectively to double-stranded DNA and forms strongly fluorescent DNA-DAPI complexes with high specificity.^[1][2][3][4] It is commonly used to detect mycoplasma in cell culture via fluorescence microscopy.^[5]

DAPI is several times more sensitive than ethidium bromide for staining DNA in agarose gels. It may be used for photofootprinting of DNA, to detect annealed probes in blotting applications by specifically visualizing the double-stranded complex, and to study the changes in DNA and analyze DNA content during apoptosis using flow cytometry. DAPI staining has also been shown to be a sensitive and specific detection method for mycoplasma.