1. To make a 5 mg/mL DAPI stock solution (14.3 mM), dissolve the contents of one vial (10 mg) in 2 mL of deionized water or dimethylformamide (DMF). Note: DAPI is not very soluble in phosphate-buffered saline (PBS).
2. For long term storage, the stock solution can be aliquoted and stored at -20°C. For short term storage, the solution can be kept at 2-6°C, protected from light. When handled properly, DAPI solutions are stable for at least six months.
3. Dilute the DAPI stock solution to 3 µM in staining buffer. A 1 mL volume will be required for each cell sample.
4. Centrifuge the cell suspension and discard the supernatant. Tap to loosen the pellet and add 1 mL of DAPI diluted in staining buffer.
5. Incubate for 15 minutes at room temperature.
6. Analyze by flow cytometry in the presence of the dye. If the cells are to be viewed by fluorescence microscopy, centrifuge the sample, remove the supernatant and resuspend cells in fresh buffer. Apply a drop of the suspension to a microscope slide, cover with a coverslip and view. For sample preparation protocols for adherent cells and suspension cells, please see the DAPI product datasheet.

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