Used in bioconjugation processes to link biomolecules such as proteins, peptides, or fluorescent dyes through click chemistry. The azide group reacts efficiently with alkynes via copper-catalyzed azide-alkyne cycloaddition (CuAAC), enabling rapid and selective coupling under mild conditions. The PEG1 spacer adds minimal hydrophilicity and flexibility, reducing steric interference while improving solubility in aqueous and organic solvents. Commonly employed in the development of diagnostic probes, targeted drug delivery systems, and surface functionalization of nanoparticles or biosensors. Its methyl ester terminus allows further modification through hydrolysis or aminolysis, making it a versatile building block in multi-step conjugation strategies.