Fluorescein isothiocyanate (FITC) is a derivative of fluorescein used in wide-ranging applications. It is the original fluorescein molecule functionalized with an isothiocyanate reactive group (-N=C=S), replacing a hydrogen atom on the bottom ring of the structure. FITC is reactive towards nucleophiles including amine and sulfhydryl groups on proteins. This mouse antibody detects the FITC only. This antibody can be coated in the plate to capture the FITC conjugated protein or antibody. Moreover, this mouse antibody used with HRP goat anti-rabbit secondary antibody, converts fluorescent signal to DAB dyeing.