Used in bioconjugation to link molecules such as peptides, proteins, or drugs with high solubility and flexibility due to the long PEG spacer. The Boc group protects the amine during synthesis and can be removed under mild acidic conditions to expose the amine for further reactions. The NHS ester end readily reacts with primary amines on biomolecules, forming stable amide bonds. Commonly applied in preparing PEGylated compounds, antibody-drug conjugates (ADCs), and functionalizing surfaces in diagnostic assays or biosensors. The extended PEG5 chain reduces steric hindrance, improving reaction efficiency and maintaining biomolecule activity.