Azido-PEG3-NHS ester is widely used in bioconjugation for linking molecules in a controlled and efficient manner. Its NHS ester group reacts readily with primary amines, such as those found on lysine residues in proteins or amine-modified nucleic acids, forming stable amide bonds. This allows for the introduction of an azide functional group onto the target molecule.

The azide group serves as a key handle for downstream click chemistry reactions, especially copper-catalyzed azide-alkyne cycloaddition (CuAAC) or strain-promoted azide-alkyne cycloaddition (SPAAC). These reactions are highly selective and bioorthogonal, making them ideal for labeling biomolecules in complex environments, including live cells.

Due to the PEG3 spacer, the reagent improves solubility and reduces steric hindrance, enhancing reaction efficiency and minimizing non-specific interactions. It is commonly used in the development of antibody-drug conjugates (ADCs), peptide modifications, surface immobilization on biosensors, and the construction of functionalized nanoparticles.

Its combination of reactivity, stability, and biocompatibility makes it a valuable tool in drug discovery, proteomics, and molecular imaging.