DRAQ5 is a novel, cell-permeant, far red-fluorescing DNA probe that excites at 647 nm and produces a fluorescence spectrum from 665 nm to beyond 780 nm, reflecting cellular DNA content. DRAQ5 can be used with FITC and RPE-labelled antibodies without requiring fluorescence compensation [1].

Mammalian cell full culture staining method [2]: (1) Cell plating: Digest and isolate cells, then resuspend in complete medium to a concentration of 2-4 × 10⁵/ml. Note: Adherent cells (such as those on coverslips or chambers) can be stained in situ, using 1-2 ml of dye per 4 cm² area. (2) Prepare staining solution: Add 4 µl of 5 mM dye stock solution per ml of medium, achieving a final concentration of 20 µM. Note: Nuclear staining is detectable at 2.5-5 µM, generally not exceeding 30 µM. (3) Fluorescent staining: Incubate at 37°C for 5-15 minutes. Caution: Avoid overstaining. (4) Washing (optional): Centrifuge at 37°C, 800 g, for 3-5 minutes, discard the supernatant, and resuspend cells at 4 × 10⁵/ml in complete medium containing 10 mM HEPES. (5) Flow cytometry: Perform dual recognition using standard pulse analysis and appropriate software to analyze parameters. (6) Laser scanning microscopy: Collect fluorescent images using a 695 nm filter. Fixed cell staining method [2]: (1) Fix cells: Use 4% paraformaldehyde in PBS for 30 minutes and resuspend in a buffer (e.g., PBS). (2) Fluorescent staining: Employ dye concentrations and conditions similar to those for live cells.