中文摘要：

采用分子模拟手段研究了功能性离子液体[HOOCBMIm]Cl修饰Porcine Pancreas脂肪酶（PPL）结构稳定性与催化性能增强的机理.在335和300 K下比较研究两种脂肪酶的一系列相互作用特点与结构性质,包括静电势（electrostatic potential,ESP）、均方根偏差（Root Mean Square Deviation,RMSD）、能量变化、溶剂化面积等等.分析结果表明：在335K下,修饰后的脂肪酶（Engineered PPL）的RMSD值（0.537？）小于未修饰的脂肪酶（Wild-type PPL）的RMSD值（0.68？）,同时Engineered PPL的自由能也低于Wild-type PPL的自由能,说明Engineered PPL的构象更加稳定.修饰剂的引入使得Engineered PPL的疏水性面积和溶剂可及性面积（Solvent Accessible Surface Area,SASA）增大,增强了Engineered PPL的稳定性和水解活力.修饰剂的正电性与修饰位点附近的负电势氨基酸形成静电吸引作用,优化了蛋白表面电荷的相互作用,进一步提高了蛋白稳定性;同时也稳定了蛋白盖子结构的打开状态,有利于底物进入蛋白空腔催化位点,实现催化活性提升.本文从分子水平展示了离子液体修饰脂肪酶并提供了一种解析化学修饰改变酶学性质的方法.

英文摘要：

Application of molecular modelling techniques to make reasonable analysis for the enzymatic properties change, reaction mechanism and further to guide the directed molecular alteration of enzymes from the molecular level is an important content of the current research in the field of enzyme engineering. While the effectiveness of ionic liquid in enhancing the stability and potency of protein pharmaceuticals has been validated for years, the underlying mechanism remains poorly understood, particularly at the molecular level. A molecular dynamics simulation was developed using a procedure that allowed a united-atom level examination of the interaction between [HOOCBMIm]＋ and a conjugated protein represented by Porcine Pancreas lipase（PPL）. Molecular dynamics（MD） simulation was performed to investigate the mechanism towards the improvement in structural stability and catalytic efficiency of the Engineered PPL by [HOOCBMIm]Cl ionic liquid. The electrostatic potential, energy change and RMSD（Root Mean Square Deviation） analysis showed the enhanced stability of engineered PPL. And the solvent accessible surface area（SASA） analysis showed the enhanced catalytic activity. The results showed that Engineered PPL＇s RMSD value（0.537 ？） was less than Wild-type PPL＇s（0.68 ？） at 335 K. This indicates that the Engineered PPL conformation becomes more stable. With binding the modifier on Wild-type PPL, we found that hydrophobicity area and SASA of Enginneerd PPL were increased. These phenomena indicate that the affinity of modifier for water generates a water layer surrounding the active center. And the electrostatic potential around the modified sites is negative before binding the modifier, that neutralization of these like charges upon modification lessens the tendency of the enzyme to unfold and also benefit for substrate into catalytic sites to enhance the catalytic activity. The results presented here provided sight into interaction between ionic liquid with the conjugated PPL at molecular