Cy7.5PEG-N3 is a fluorescent azide dye, known as CY7.5 azide, designed for use with amines in peptides, proteins, and oligonucleotides. This compound is a click chemistry reagent, featuring an azide group that enables copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with alkyne-containing molecules. Additionally, it can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) reactions with molecules possessing DBCO or BCN groups. The dye exhibits excitation/emission peaks at 770/820 nm.