DAPI (HCl), 10mg

STEMCELL Technologies offers DAPI (Hydrochloride), a blue-fluorescent dye widely used to detect nuclei in fluorescence microscopy. The dye binds to AT-rich regions of double-stranded DNA, with binding accompanied by an ~20-fold enhancement in fluorescence that is directly proportional to the amount of DNA present. It has an emission maximum at ~454 nm, and the resulting complex remains stable for several hours at room temperature over the pH range 4–11. DAPI can also bind to RNA through AU-selective intercalation; the DAPI/RNA complex emits at ~500 nm with only an ~20% increase in quantum yield.

In multicolor fluorescence applications, DAPI serves as a counterstain whose blue fluorescence contrasts vividly with red, yellow, or green fluorescent dyes. It has also been used for studying apoptosis (at low concentrations the dye is excluded from live cells but penetrates dead or damaged cells), and in quantitative DNA assays, in situ hybridization, chromosome sorting, and mycoplasma detection assays.

The chemical formula is C₁₆H₁₅N₅ · 2HCl with a molecular weight of 350.3 g/mol. Excitation occurs at 358 nm for the DNA complex and 340 nm for the free form; emission occurs at 454 nm (DNA complex), 488 nm (free form), and 500 nm (RNA complex). Supplied as a crystalline solid, the product should be stored at –20°C and protected from prolonged exposure to light. Verified applications include imaging and non-imaging flow cytometry, fluorescence microscopy, electrophoresis, fluorescence in situ hybridization (FISH), fluorometry, genomic in situ hybridization (GISH), and NMR.