calcein


calcein

A chelating agent which fluoresces brightly in the presence of bound Ca2+. The acetomethoxy derivative of calcein is used as a temporary label to test cell viability: once the calcein acetomethoxy complex enters healthy cells, intracellular esterases remove the acetomethoxy group, which fluoresces bright green—apparently in protest—something that dead cells, which lack esterases, cannot do.