The galactosidase substrate, DDAO galactoside 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 and the hydrolysis product is over 200 nm, along the two species to be easily distinguished.

To make a concentrated stock solution of up to 5 mg/mL, dissolve in high quality anhydrous DMSO. Store frozen, desiccated and protected from light.