Propargyl-PEG3-NHS ester is widely used in bioconjugation and chemical biology research. Its primary application lies in linking biomolecules, such as proteins, peptides, or antibodies, to other functional groups or surfaces. The NHS ester group reacts efficiently with primary amines, enabling covalent attachment to biomolecules, while the propargyl group allows for further modification via click chemistry, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC). This makes it valuable in creating labeled probes for imaging, diagnostics, and drug delivery systems. Additionally, it is employed in the development of bioconjugates for targeted therapies, where precise molecular interactions are critical. Its PEG spacer enhances solubility and reduces steric hindrance, improving the efficiency of conjugation reactions.