Fluorescein isothiocyanate molecule Ilustración e icono

A ball-and-stick chemical diagram depicts an organic fluorophore with a xanthene-based fluorescein scaffold bearing an isothiocyanate (N=C=S) functional group. In biochemistry and molecular imaging, this compound, FITC (fluorescein isothiocyanate), serves as a reactive dye that forms stable thiourea linkages with primary amines, enabling labeling of proteins and antibodies for fluorescence microscopy and flow cytometry. The illustration shows hierarchical structure: an isothiocyanate substituent integrated into the larger aromatic ring system of the dye molecule.