Used in bioconjugation processes to link biomolecules such as peptides, proteins, and antibodies with other functional groups, especially in drug delivery systems and diagnostic probes. The azide group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient and selective coupling with alkyne-containing compounds. The carboxylic acid group allows for amide bond formation with amine-containing molecules after activation (e.g., using EDC/NHS). The dual PEG spacers enhance water solubility, reduce aggregation, and improve the biocompatibility of conjugates. Commonly applied in the development of antibody-drug conjugates (ADCs), fluorescent labeling, and surface immobilization in biosensors. Also utilized in PEGylation strategies to extend the circulation half-life of therapeutic molecules.