Alkyne-PEG5-SNAP is a chemical reagent characterized by its alkyne group. This compound can conjugate with benzyl guanine (BG), where the BG moiety undergoes a specific and rapid reaction with the SNAP-tag (a type of peptide protein tag), facilitating irreversible and covalent labeling of SNAP fusion proteins, and provides additional alkyne functionality for further coupling. Additionally, Alkyne-PEG5-SNAP serves as a click chemistry reagent that interacts with molecules containing azide groups through a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC).