Fluorescent probe and cell staining dye. Reacts with primary and secondary amine groups on proteins and other biomolecules. Cell permeable and covalently couples, via its succinimidyl group, to intracellular molecules. Due to this covalent coupling reaction fluorescent CFSE can be retained within cells for extremely long periods. Used for immunological studies to monitor the proliferation of many cell types (including lymphocytes, fibroblasts) and even bacteria. Has been used to prepare fluorescent derivatives of tubulin and for the preparation of a phenytoin tracer for the determination of this drug in serum and plasma by fluorescence polarization immunoassay (FPIA). Favored over FITC in bioconjugations, since FAM reagents are more resistant to hydrolysis. In addition, FAM reagents require less stringent conjugation conditions and give better conjugation yields, and the resulted conjugates have superior stability. Spectral properties: lambdaex= 492; lambdaem=517nm in DMF or 0.1 M Tris, pH 8.0.