Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model-Free Approach.
Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model-Free Approach.
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使用分子动力学模拟和无模型方法相结合来预测溶致液晶的 EPR 光谱。
DOI：
10.1002/chem.201702682
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Prior C
中科院分区：
文献类型：
--
作者：
Prior C
我们报告了完全原子分子动力学（MD）模拟的首次应用，以预测掺杂顺磁自旋探针的不同聚集态溶致液晶的运动电子顺磁共振（EPR）光谱。这项研究的目的是双重的。首先，考虑到 EPR 谱对溶致聚集体中掺杂的自旋探针的运动和顺序高度敏感，根据 MD 建模结果模拟 EPR 线形状为目前用于模拟此类系统的力场提供了最终的测试平台。其次，使用无模型 (MF) 方法从 MD 轨迹中提取的运动参数来模拟 EPR 线形状。因此，组合的 MD-EPR 方法使我们能够直接测试 MF 方法在多组分分子运动系统中应用的有效性。使用通用 AMBER 力场 (GAFF) 对十二烷基硫酸钠 (SDS) 和十二烷基三甲基氯化铵 (DTAC) 液晶进行了全原子 MD 模拟。由此产生的 MD 轨迹用于预测和解释预胶束、胶束、棒状和层状聚集体的 EPR 光谱。预测的 EPR 谱与大多数实验线形状吻合良好，从而证实了所研究系统所采用的力场和 MF 方法的有效性。同时模拟结果证实 GAFF 倾向于高估表面活性剂分子羰基链的堆积和顺序。
We report the first application of fully atomistic molecular dynamics (MD) simulations to the prediction of the motional electron paramagnetic resonance (EPR) spectra of lyotropic liquid crystals in different aggregation states doped with a paramagnetic spin probe. The purpose of this study is twofold. First, given that EPR spectra are highly sensitive to the motions and order of the spin probes doped within lyotropic aggregates, simulation of EPR line shapes from the results of MD modelling provides an ultimate test bed for the force fields currently employed to model such systems. Second, the EPR line shapes are simulated using the motional parameters extracted from MD trajectories using the Model‐Free (MF) approach. Thus a combined MD‐EPR methodology allowed us to test directly the validity of the application of the MF approach to systems with multi‐component molecular motions. All‐atom MD simulations using the General AMBER Force Field (GAFF) have been performed on sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) liquid crystals. The resulting MD trajectories were used to predict and interpret the EPR spectra of pre‐micellar, micellar, rod and lamellar aggregates. The predicted EPR spectra demonstrate good agreement with most of experimental line shapes thus confirming the validity of both the force fields employed and the MF approach for the studied systems. At the same time simulation results confirm that GAFF tends to overestimate the packing and the order of the carbonyl chains of the surfactant molecules.