Cy3-PEG-N3 (MW 5000) is a fluorescent dye known as Cy3 azide, specifically designed for peptide, protein, and oligonucleotide amino groups. As a click chemistry reagent, it contains an azide group, enabling copper-catalyzed azide-alkyne cycloaddition (CuAAC) with alkyne-containing molecules. Additionally, it can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing either DBCO or BCN groups.