Used in bioconjugation processes, particularly in the development of antibody-drug conjugates (ADCs). Its PEG4 spacer improves solubility and reduces aggregation, while the (2-pyridyldithio) group enables reversible disulfide bond formation with thiol-containing molecules. Commonly employed to link cytotoxic agents to targeting antibodies, allowing controlled release of the drug in reducing environments such as inside cells. Also applied in immobilizing biomolecules on surfaces for biosensors and diagnostic assays due to its stable yet cleavable linkage.