Used in bioconjugation for linking biomolecules due to its long hydrophilic PEG spacer, which enhances solubility and reduces aggregation. The propargyl group enables click chemistry reactions, especially copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient attachment to azide-containing molecules. Commonly applied in drug delivery systems, surface functionalization of nanoparticles, and development of PEGylated peptides or proteins to improve stability and circulation time. Also utilized in creating bioactive probes and diagnostic agents where controlled spacing and orientation are critical.