Procedures for synthesis of hemin-N-oxysuccinimide ester. To dried hemin (100 mg, 0.154 mmol., 1.0 eq.), DMSO (3 mL) was added under a nitrogen atmosphere with stirring for one hour at room temperature with the exclusion of light. To this solution, EDC (147.6 mg, 0.77 mmol., 5.0 eq.) and NHS (44.4 mg, 0.386 mmol., 2.5 eq.) were added. The mixture was stirred further under a nitrogen atmosphere for one hour at room temperature. The final product was precipitated by its addition to a saturated NaCl solution (6 mL), followed by adding diethyl ether (24 mL), mixing and vacuum filtration.