ICG PEG N3 (MW 1000) is an indocyanine green (ICG) azide fluorescent dye used for labeling amines in peptides, proteins, and oligonucleotides. It serves as a click chemistry reagent with an azide group that participates in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with molecules containing an alkyne group. It can also engage in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules having DBCO or BCN groups (Ex/Em = 785/813 nm).