Coelenterazine (UltraPure grade)

Calcium measurement is critical for numerous biological investigations. The aequorin complex comprises a 22 kD apoaequorin protein, molecular oxygen and the luminophore coelenterazine. When three Ca2 ions bind to this complex, coelenterazine is oxidized to coelenteramide, with a concomitant release of carbon dioxide and blue light. The approximately third-power dependence of aequorin's bioluminescence on Ca2 concentration allows the measurement of Ca2 concentrations with a broad detection range from about 0.1 µM to >100 µM. Unlike fluorescent Ca2 indicators, Ca2+bound aequorin can be detected without illuminating the sample, thereby eliminating interference from autofluorescence. Native coelenterazine and its derivatives confer different Ca2 affinities and spectral properties on the aequorin complex. Recombinant apoaequorin reconstituted with coelenterazine hcp is reported to have the best luminescence overall, with both a high quantum yield and a fast response time. However, intracellular reconstitution of aequorin from coelenterazine analogs can be relatively slow. Aequorins containing the cp, f or h form of coelenterazine exhibit 10?20 times stronger luminescence than that of apoaequorin reconstituted with native coelenterazine. Coelenterazines h and cp has been used in HTS screening assay for GPCRs.