Propargyl-PEG3-SH is widely used in bioconjugation and click chemistry applications. Its thiol group allows for selective reactions with maleimides or other thiol-reactive groups, making it valuable for modifying proteins, peptides, or surfaces. The propargyl group enables efficient participation in copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, a cornerstone of click chemistry, facilitating the attachment of biomolecules or functional groups. This compound is particularly useful in drug delivery systems, where it helps create targeted conjugates, and in material science for surface functionalization. Its PEG spacer enhances solubility and reduces steric hindrance, improving reaction efficiency in biological and chemical systems.