Used in bioconjugation processes to link biomolecules such as peptides, proteins, and antibodies with other functional groups, especially in drug delivery and diagnostic applications. The azide group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient and selective coupling under mild conditions. The long PEG9 spacer provides flexibility, improves solubility, and reduces steric hindrance, enhancing binding efficiency. Commonly applied in the development of PEGylated compounds, targeted therapies, and surface modifications of nanoparticles or biosensors. Also utilized in research settings for labeling and tracking biomolecules in cellular systems.