Used in bioconjugation processes to modify proteins and peptides by introducing a hydroxybenzoate handle for further coupling. Commonly employed in the development of antibody-drug conjugates (ADCs) and labeling of biomolecules for diagnostic assays. Its NHS ester group reacts efficiently with primary amines on proteins, forming stable amide bonds, while the phenolic hydroxyl group allows for subsequent functionalization via electrophilic substitution or activation. Also applied in surface modification of nanoparticles and biosensors where controlled immobilization of biomolecules is required.