6-Carboxyfluorescein diacetateMolecular weight: 460.396-CFDA is not fluorescent until deacetylated by esterase enzymes. Since only viable cells can deacetylate 5-CFDA, it is utilized in assays of viable cellsλex = 492 nm; λem = 517 nm in 0.1 M Tris pH 8.0 (esterase)