Used in bioconjugation processes to link biomolecules such as peptides, proteins, and antibodies with high specificity. The azide group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient and selective coupling under mild conditions. The PEG5 spacer provides water solubility, reduces aggregation, and increases flexibility between conjugated molecules, enhancing binding efficiency and biological activity. Commonly applied in the development of antibody-drug conjugates (ADCs), diagnostic probes, and targeted therapeutics. Also utilized in surface functionalization of nanoparticles and biosensors where controlled immobilization is required. Its hydrophilic nature helps improve pharmacokinetic properties in vivo when used in prodrugs or imaging agents.