DAPI (4',6-Diamidino-2-Phenylindole, dihydrochloride) is a popular blue DNA dye that is used as a nuclear counterstain in fluorescence microscopy, chromosome staining and flow cytometry. The dye binds to the minor groove of dsDNA with approximately 20-fold fluorescence enhancement, with higher affinity for A-T rich regions. Also see DAPI dilactate, a more water soluble form of the dye.    Classic blue nuclear counterstain for fixed cells  Can be used at higher concentrations to stain live cells  &lamba;Ex/&lamba;Em = 358/461 nm (with DNA)  Off-white solid soluble in H2O  Store at 4°C and protect from light, especially in solution  C16H17Cl2N5  MW = 350.25  [28718-90-3]