FITC-PEG-N3 (MW 3400) is a fluorescent dye that combines polyethylene glycol (PEG) with fluorescein isothiocyanate (FITC) and contains an azide group. It serves as a click chemistry reagent, engaging in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with alkyne-containing molecules. Additionally, it participates in strain-promoted alkyne-azide cycloaddition (SPAAC) reactions with molecules containing DBCO or BCN groups.