Used in bioconjugation processes, particularly in the development of antibody-drug conjugates (ADCs) and targeted therapeutics. The azide group enables click chemistry reactions, such as copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient and selective coupling with alkyne-functionalized biomolecules. The disulfide (SS) linker provides a cleavable bond that is stable in circulation but breaks under reducing conditions inside cells, enabling controlled release of payloads like drugs or imaging agents. The PEG2 spacer improves solubility, reduces aggregation, and enhances the pharmacokinetic properties of the conjugate. The terminal carboxylic acid allows for further activation and amide bond formation with amines on proteins, peptides, or other molecules, making it a versatile building block in the design of complex bioconjugates.