Luminescent Calcium Detection

Coelenterazine and Its Analogs

A Ca2+-binding protein, aequorin, can be found in the jellyfish Aequorea victoria umbrella’s outer margin. This photoprotein consists of an apoprotein (apoaequorin), molecular oxygen and coelenterazine. Aequorin contains three binding sites for calcium. When calcium ions bind to these sites, they catalyze the oxidation of coelenterazine to coelenteramide, releasing a blue-fluorescent protein product1-3. The major advantages of using coelenterazine and its analogs for calcium detection include the elimination of autofluorescence, photobleaching and biological degradation since they do not require light excitation. Additionally, they offer a wide detection range 4,5.

Coelenterazine and its analogs have been used in transgenic cells expressing apoaequorin for the detection of Ca2+. The Renilla luciferase also oxidizes coelenterazine and its analogs to yield a blue fluorescent protein.

AnaSpec offers the following coelenterazines (native and analogs) which have different Ca2+ sensitivities and emission wavelengths:
Other Calcium Detection Reagents:

To request AnaSpec’s 2006-2007 Detection Reagents & Kits catalog, click here

* AnaSpec also offers custom synthesis of fluorescent probes, for more information, please contact


  1. Shimomura, O. and FH. Johnson, Proc. Natl. Acad. Sci. USA 75, 2611 (1978).
  2. Shimomura, O. and FH. Johnson, Nature 256, 236 (1975).
  3. Shimomura, O. et al. Biochem. J. 296 (Pt 3), 549 (1993).
  4. Burton, M. et al. Free Radic. Res. 37, 145 (2003).
  5. Shiomomura, O. and K. Teranishi, Luminescence 15, 51 (2000).