Used in bioconjugation reactions, particularly in click chemistry applications, due to its strained alkyne group that reacts rapidly and selectively with azides without the need for a catalyst. The PEG3 spacer enhances water solubility and improves the pharmacokinetic properties of conjugated molecules, making it suitable for labeling biomolecules, developing antibody-drug conjugates, and modifying peptides or proteins for diagnostic or therapeutic use. The terminal carboxylic acid allows for easy coupling to amines, enabling stable amide bond formation with targeting ligands or fluorescent tags. Commonly employed in drug delivery systems, imaging probes, and multifunctional scaffolds in biomedical research.