What is 7-AAD used for?

7-aminoactinomycin D (7-AAD) is a membrane impermeant fluorescent dye with a strong affinity for double-stranded DNA. It intercalates selectively at GC-rich regions of DNA. 7-AAD bound to DNA has a large Stokes shift with excitation/emission at 546/647 nm.

7-AAD is useful for multicolor fluorescence microscopy and flow cytometry and for chromosome banding studies. It stains necrotic and late apoptotic cells with compromised membrane integrity but is generally excluded from live cells and early apoptotic cells because of its membrane impermeability.