Performance Of Polyethylene Glycol Derivatives And Its Several Modifying Enzymes

As an effective technique to improve part of the characteristics, such as enzyme activity, thermal stability of an enzyme, enzyme chemical modification has received considerable attention. Several PEG derivatives (modifier) with different molecular weight and structure were synthesized in this dissertation, by which Trypsin and Cholesterol Esterase were modified, and relative characteristics of the two enzymes modified were determined.It has been discovered in this thesis that the method of PEG-SS and PEG-Potassium tert-butylate to synthesize single chain modifier are superior to that of PEG-Sodium-Naphthaline, because the latter requires five steps and purification of the product is complicated, and the same as the synthesis of, the method with NPC(nitrophenyl chloroformate) was adopted.Eight PEG derivatives synthesized were used to modify Trypsin and. The Enzyme activity of Trypsin is retained to a great degree through modification, and the thermal stability is improved greatly, too. And it is proved that the thermal stability is related directly with the dimensional structure of enzyme. The results showed that the loss of Enzyme activity of Cholesterol Esterase was related to the molecular weight and structure, and the less loss of Enzyme activity were acquired only through modification by double chain modifiers.