Propargyl-PEG12-amine is a heterobifunctional reagent that enables amide formation with carboxylic acids, activated NHS esters, carbonyls (ketone, aldehyde) etc. The propargyl group is reactive with azide compounds via copper catalyzed azide-alkyne Click Chemistry to yield a stable triazole linkage. The PEG units enhance the hydrophilicity of the molecule in aqueous media.