Used as a key reagent in click chemistry, particularly in bioconjugation applications. Its azide group readily participates in copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, enabling efficient labeling and coupling of biomolecules such as proteins, peptides, and nucleic acids. The polyethylene glycol (PEG) spacer enhances solubility in aqueous and organic solvents, reduces nonspecific binding, and improves the flexibility and accessibility of the reactive azide group. The 2-nitropyridine moiety can act as a chromophore or be used in photoreactive systems, allowing for light-triggered reactions or detection. Commonly employed in the development of diagnostic probes, targeted drug delivery systems, and functionalized surfaces for biosensors and microarrays.