fluorescein isothiocyanate

Fluorescein isothiocyanate (FITC) is a synthetic organic compound and a derivative of fluorescein functionalized with an amine-reactive isothiocyanate group (−N=C=S). It emits bright green fluorescence when excited by blue light (excitation peak ~495 nm; emission peak ~519–520 nm)[2][4][8]. FITC covalently binds to primary amines on proteins and other biomolecules via its reactive isothiocyanate group to form stable thiourea bonds. This property makes it widely used as a fluorescent labeling reagent in biochemistry and molecular biology for applications such as flow cytometry, immunofluorescence microscopy, immunoassays (ELISA), fluorescence in situ hybridization (FISH), protein detection in gels/Western blots, and cell tracking. FITC can be supplied as either of two positional isomers—fluorescein 5-isothiocyanate or fluorescein 6-isothiocyanate—or as a mixture. Its main limitation compared to newer dyes like Alexa Fluor or DyLight series is photobleaching susceptibility[2][4]. FITC itself does not have therapeutic effects; it serves exclusively as a diagnostic/research tool.

Other names

fluorescein isothiocyanate isomer Ifluorescein-5-isothiocyanatefluorescein5-isothiocyanatefluorescein 5-isothiocyanateSpiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one, 3',6'-dihydroxy-5-isothiocyanato-2-(6-hydroxy-3-oxo-(3H)-xanthene-9-yl)-5-isothiocyanato benzoic acid