Researchers are always on the lookout for more sensitive conjugates for use in bioassays. The bioluminescent photoprotein aequorin is proving to be a useful alternative to traditional enzyme tags in ELISA-type immunoassays. SeaLite Sciences, Inc., of Bogart, Ga., manufactures a fully active, recombinant form of aequorin under the trademark AquaLite and sells a number of different useful derivatives and conjugates, including AquaLite® Biotin and AquaLite® Streptavidin.
Aequorin is a 22 kDa protein complex from the jellyfish Aequorea victoria; it contains bound oxygen, the luciferin coelenterazine, and three calcium binding sites. Upon addition of calcium ions, aequorin undergoes conformational changes that result in the oxidation of coelenterazine by the protein-bound oxygen. As diagrammed below, the energy from this oxidation reaction is released as a flash of blue light, centered at 469 nm.
Calcium Light Production from Aqualite®