Coelenterazine (native form) is a luminescent enzyme substrate for apoaequorin and Renilla luciferase. The aequorin complex has been used as an excellent calcium indicator that can measure a broad concentration range of calcium from ~0.1 uM to >100 uM. Renilla luciferase has been widely used as a reporter protein. Renilla luciferase/coelenterazine has also been used as the bioluminescence donor in bioluminescence resonance energy transfer (BRET) to study protein-protein interactions. Other uses of coelenterazine include chemiluminescent detection of superoxide anion and peroxynitrite in cells or tissues. Also see water soluble Aquaphile™ Coelenterazine.