Polyethylene Glycol Derivatives And Their Chemically Modified Trypsin

Poly(ethylene glycol) derivatives with well solubility, biocompatibility and immunogenicity are applied to chemical modification of biomacromolecule extensively. In this paper poly(ethylene glycol) and monomethoxypoly(ethylene glycol) with different molecular weight were used as raw material. A series of PEG derivatives were prepared by different synthetic methods: PEG-SS, mPEG-SS, mPEG-CS, BmPEG. The synthetic products were characterized by infrared spectrum analysis and nuclear magnetic resonance instrument. The results of characterization are consistent with the structures of the products. Especially the NMR spectrum of the branched reagent accords with the assigned structure. For protein modification, modificators was activated as the succinymidyl ester. Then under certain condition,trypsin was modified by the products. A comparison of modified enzymes and native enzyme was carried out for activity, pH and temperature stability, K_m value. The results show that temperate modification can cause enzyme's activity increased, but the activities of most modified enzymes are lower than native's. The characterization presented in this paper provides strong testimony to the fact that attachment of PEG to trypsin improves the thermal stability of the enzyme. The modification does not change the optimum pH value of trypsin. The K_m values of the conjugates are slightly higher than the native enzyme.