ICG PEG N3 (MW 3400) is an indocyanine green (ICG) azide fluorescent dye utilized for labeling amines in peptides, proteins, and oligonucleotides. As a click chemistry reagent, it contains an azide group that can undergo a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC) with alkyne-containing compounds. Additionally, it can participate in a strain-promoted azide-alkyne cycloaddition reaction (SPAAC) with molecules that have DBCO or BCN groups, exhibiting excitation/emission wavelengths of 785/813 nm.