Fmoc-N-amido-PEG3-azide is a PROTAC linker belonging to the PEG class, used in PROTAC molecule synthesis. It functions as a click chemistry reagent and contains an azide group, allowing it to participate in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with alkyne-containing molecules. Additionally, it can undergo strain-promoted azide-alkyne cycloaddition (SPAAC) with molecules containing DBCO or BCN groups.