9H-(1,3-DICHLORO-9,9-DIME 5 MG，D6487，Invitrogen

The phosphatase substrate DDAO phosphate [9H-(1,3-dichloro-9,9-dimethylacridin-2-one-7-yl) phosphate, diammonium salt] yields a hydrolysis product that can be excited with the 633 nm laser (excitation/emission maxima ~645/660). Although the substrate itself is fluorescent (excitation/emission maxima ~460/610 nm), the difference between the substrate's excitation maximum and that of its hydrolysis product is over 200 nm, allowing the two species to be easily distinguished.