Simulated revelation of the adsorption behaviours of acetylcholinesterase on charged self-assembled monolayers
Simulated revelation of the adsorption behaviours of acetylcholinesterase on charged self-assembled monolayers
复制标题
带电自组装单分子层上乙酰胆碱酯酶吸附行为的模拟揭示
DOI：
10.1039/c9nr10123c
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发表时间：
2020
期刊：
影响因子：
6.7
通讯作者：
Zhou Jian
中科院分区：
文献类型：
--
作者：
Yang Shengjiang;Liu Jie;Zheng He;Zhong Jinyi;Zhou Jian
基于乙酰胆碱酯酶（AChE）的电化学生物传感器具有操作简单、快速、可靠、成本低等优点，是检测有机磷农药和氨基甲酸酯类农药的一种新方法。固定在电极表面的乙酰胆碱酯酶的生物活性以及酶与电极之间的直接电子转移（DET）速率直接决定了乙酰胆碱酯酶生物传感器的分析性能，实验研究表明，电极表面的荷电对乙酰胆碱酯酶生物传感器的检测能力有很大影响。因此，在分子水平上揭示乙酰胆碱酯酶在本体溶液和带电表面上的行为是非常重要的。采用平行回火蒙特卡罗（PTMC）和全原子分子动力学模拟（AAMD）方法，研究了加利福尼亚电鳐乙酰胆碱酯酶（TcAChE）在表面电荷密度不同的带相反电荷的自组装单分子膜（COOH-SAM和NH 2-SAM）上的吸附取向和构象.模拟结果表明，TcAChE在电偶极子和带电残基片的协同作用下，能够自发稳定地吸附在两个带相反电荷的表面上，且吸附方向相反. TcAChE吸附在带正电的表面时，其活性位峡谷以“端对”的方式朝向表面，活性位靠近表面，基底的隧穿成本低于带负电的表面和本体溶液中的隧穿成本;而吸附在带负电的表面时，TcAChE的活性位点远离表面，并且活性位点峡谷以“背对”取向朝向溶液。这表明，带正电的表面可以提供一个更好的微环境，有效的生物催化反应和快速DET TcAChE与电极表面。RMSD、RMSF、偶极矩、回转半径、离心率和叠加结构表明，TcAChE相对柔性的结构在模拟过程中只发生了轻微的构象变化，吸附后的天然构象得到了很好的保留.本工作有助于我们更好地理解TcAChE在荷电表面上的吸附机理，并可能为开发基于TcAChE的新型安培生物传感器检测有机磷农药提供指导。
An acetylcholinesterase (AChE)-based electrochemical biosensor, as a promising alternative to detect organophosphates (OPs) and carbamate pesticides, has gained considerable attention in recent years, due to the advantages of simplicity, rapidity, reliability and low cost. The bio-activity of AChE immobilized on the surface and the direct electron transfer (DET) rate between an enzyme and an electrode directly determined the analytical performances of the AChE-based biosensor, and experimental studies have shown that the charged surfaces have a strong impact on the detectability of the AChE-based biosensor. Therefore, it is very important to reveal the behaviour of AChE in bulk solution and on charged surfaces at the molecular level. In this work, the adsorption orientation and conformation of AChE from Torpedo californica (TcAChE) on oppositely charged self-assembled monolayers (SAMs), COOH-SAM and NH2-SAM with different surface charge densities, were investigated by parallel tempering Monte Carlo (PTMC) and all-atom molecular dynamics simulations (AAMD). Simulation results show that TcAChE could spontaneously and stably adsorb on two oppositely charged surfaces by the synergy of an electric dipole and charged residue patch, and opposite orientations were observed. The active-site gorge of TcAChE is oriented toward the surface with the “end-on” orientation and the active sites are close to the surface when it is adsorbed on the positively charged surface and the tunnel cost for the substrate is lower than that on the negatively charged surface and in bulk solution, while for TcAChE adsorbed on the negatively charged surface, the active site of TcAChE is far away from the surface and the active-site gorge is oriented toward the solution with a “back-on” orientation. It suggests that the positively charged surface could provide a better microenvironment for the efficient bio-catalytic reaction and quick DET between TcAChE and the electrode surface. Moreover, the RMSD, RMSF, dipole moment, gyration radius, eccentricity and superimposed structures show that only a slight conformational change occurred on the relatively flexible structure of TcAChE during simulations, and the native conformation is well preserved after adsorption. This work helps us better comprehend the adsorption mechanism of TcAChE on charged surfaces and might provide some guidelines for the development of new TcAChE-based amperometric biosensors for the detection of organophosphorus pesticides.