Used in bioconjugation for labeling and detecting biomolecules through click chemistry. The azide group reacts selectively with alkynes via copper-catalyzed azide-alkyne cycloaddition (CuAAC), enabling efficient attachment to proteins, nucleic acids, or cell surfaces. PEG5 spacer enhances solubility and reduces steric hindrance, improving reaction efficiency and accessibility to target sites. Commonly applied in fluorescence imaging, protein pull-down assays, and development of diagnostic probes. Also utilized in drug discovery for constructing biotinylated compound libraries, where streptavidin-based detection or purification is required. Suitable for both in vitro and in vivo applications due to its stability and biocompatibility.