D-Luciferin potassium salt is the water-soluble potassium salt form of D-Luciferin. D-Luciferin is the substrate for the enzyme Firefly Luciferase. It can produce bioluminescence through oxidation by the enzyme luciferase. The typical emission spectrum for luciferase is in the yellow-green region (550–570 nm), with a peak at 562 nm at basic media (pH~7.5–7.8)[1]. For D-Luciferin potassium salt possesses water solubility, it is usually in in vivo bioluminescence imaging[2].