功能化离子液体修饰多壁碳纳米管固定化Candida antarctic lipase B

Study of Surface Modifications of Multiwalled Carbon Nanotubes by Functionalized Ionic Liquid to Immobilize Candida antarctic lipase B

将带不同阴离子(Br^-、BF_4^-、PF_6^-、H_2PO_4^-)的咪唑离子液体修饰改性的多壁碳纳米管(MWNTs)作为一种全新的载体通过物理吸附法固定化褶皱假丝酵母脂肪酶B(CALB),对其酶学性能进行测试。并通过透射电镜、拉曼光谱、热重分析、X射线光电子能谱对修饰前后的MWNTs进行表征,研究材料表面修饰对酶学性能的影响。研究结果表明,经过离子液体表面修饰后的MWNTs固定化CALB具有更高的比活力,耐受性(高温、高pH值)、热稳定性和重复使用性也得到进一步增强;离子液体中不同的阴离子对修饰MWNTs固定化酶的酶学性能有显著影响,其中以PF_6^-为阴离子的固定化酶比活力最高,比未修饰的MWNTs提高了5倍。固定化酶的动力学参数分析表明离子液体的引入增强了酶与底物之间的亲和力,从而增强了酶的活性。

Multiwalled carbon nanotubes modified on the surface by imidazole ionic liquids with different types of anions （Br-, BF4-, PF6- or H2PO4-） as a new-generation carrier were fabricated. Subsequently, Candida antarctic lipase B （CALB） was immobilized on the functionalized MWNTs via physical attachment, and its enzymology properties were tested. The morphology of the MWNTs before and after the modification was determined by transmission electron microscopy （TEM）, Raman spectroscopy, thermo gravimetric analysis （TGA）, and X-ray photoelectron spectroscopy （XPS）. These characterizations were used to study the influence of surface modification of materials on the enzymatic properties. The results revealed that CALB immobilized on MWNTs modified by ionic liquids not only had a higher specific activity as compared with that of CALB immobilized on pure MWNTs, but also better tolerance （high temperature, high pH）, thermostability, and reusability. The different anions of ionic liquids, which were used to modify MWNTs, exert a remarkable effect on the properties of immobilized enzyme. The specific activity of MWNTs-IL （PF~）-CALB were the highest and were five times higher than that of MWNTs-CALB with no modification. The analysis of kinetic parameters of immobilized enzymes showed that the modification of ionic liquids for carriers enhanced the affinity between the enzyme and the substrate, so as to increase the enzyme activity.