Synthesis And Properties Of The PEG Derivative

More and more rotein and peptides have been applied in various treatment of disease. But protein and peptides drugs may induce strong immune response, have a short circulating life and are rapidly degraded. Chemical modification, one of the newly developed technology, can change the unfavorable characteristics. This study contains the process optimization in synthesis of mPEG-NHS, process optimization in modification of the model protein, separation of the modified protein by the chromatography method.The synthesis of mPEG-NHS is achieved via two chemical reactions.The first step is to synthesize mPEG-SA from the mPEG and Succinic anhydride;The second step is to synthesize mPEG-NHS from the mPEG-SA and NHS using DCCI (N.N'-Dicyclohex ) as catalyst.The results of the process optimization showed that the higher transformation rate and higher purity is achieved.And the optimum reaction conditions were as follows: (1) the first reaction: using pyridine as catalyst;the ration of succinic anhydride and mPEG 10:1;the reaction time 3h;(2)the second reaction :the ration of mPEG-SA and NHS 1: 2.5,the temperature 40℃ ,the reaction time 25h. In this case,the transformation rate of the two reaction were 60.1% and 56.0%.The modification rate is affected by the reaction conditions.The optimization of the reaction condition can enhance the modification rate. And the optimum reaction conditions were as follows:the reaction time 10 min,the the ration of proteins and mPEG-NHS l:5,using sodium tetraborate decahydrate solution (pH=9.0)as the buffer.Under these conditions,the modification rate was 47.5%.The modified protein and the unmodified protein can be separated by the chromatography method . The modified egg white lysozyme was separated by the sephadex G-75 and Deae-sepharose CL-6B(cation-exchange chromatography);The modified BSA was separated by the sephadex G-100 and Q-Sepharose(anion-exchange chromatography).The results of SDS-PAGE showed that the modified protein and the unmodified protein was separated.