This compound is an N-hydroxysuccinimide (NHS) ester used primarily as a labeling reagent in bioconjugation. It reacts selectively with primary amine groups (e.g., lysine residues) on peptides, proteins, and biomolecules to form stable amide bonds, attaching the chromophoric (E)-4-((4-(dimethylamino)phenyl)diazenyl)benzoyl group. This azo dye moiety enables UV-Vis detection and visualization, making it ideal for preparing labeled peptides and proteins in diagnostic, imaging, and pharmaceutical applications. Commonly employed in solid-phase peptide synthesis, bioconjugation protocols, functionalization of polymers, and modification of biomolecules for research and therapeutic uses. Its stability minimizes side reactions, ensuring high yields and specificity without racemization concerns during conjugation.