Propargyl-PEG4-5-nitrophenyl carbonate is heterobifunctional reagent with a propargyl group and nitrophenyl group. The propargyl group enales the formation of triazole linkage with azide compounds or biomolecules via copper catalyzed Click Chemistry. Nitrophenyl group is reactive towards the amino group of lysine by means of stable urethane linkages. The PEG units enhance the solubility of the molecule in aqueous media.