Used in bioconjugation to link biomolecules such as peptides, proteins, or antibodies with high selectivity and efficiency. The endo-BCN group reacts rapidly with azide-functionalized compounds via strain-promoted alkyne-azide cycloaddition (SPAAC), enabling bioorthogonal ligation without interfering with biological processes. The PEG2 spacer improves solubility and reduces steric hindrance, enhancing reaction kinetics and accessibility in complex biological environments. The NHS ester end reacts readily with primary amines on biomolecules, forming stable amide bonds. Commonly used in labeling, imaging, drug delivery systems, and the development of antibody-drug conjugates (ADCs) where minimal non-specific binding and fast conjugation are critical. Suitable for both in vitro and in vivo applications due to its stability and biocompatibility.