Used in bioconjugation processes to link molecules such as proteins, peptides, or antibodies with other compounds like fluorescent dyes, drugs, or nanoparticles. The NHS ester group reacts efficiently with primary amines (e.g., lysine residues or N-terminal amines) under mild conditions, forming stable amide bonds. The N3 (azide) group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing modular and selective attachment to alkyne-bearing molecules. Commonly applied in the development of antibody-drug conjugates (ADCs), diagnostic probes, and functionalized biomaterials. Its dual functionality supports sequential or orthogonal conjugation strategies in complex biological labeling and drug delivery systems.