Luciferin is a common bioluminescent reporter used for in vivo imaging of the expression of luciferase. This water soluble substrate for the firefly luciferase enzyme utilizes ATP and Mg2+ as cofactors to emit a characteristic yellow-green emission in the presence of oxygen, which shifts to red light in vivo at 37C. Through the utilization of ATP, the reaction can be further used to indicate the presence of energy or life in order to function as a life-death stain.
