Prediction of EPR Spectra of Liquid Crystals with Doped Spin Probes from Fully Atomistic Molecular Dynamics Simulations: Exploring Molecular Order and Dynamics at the Phase Transition
Prediction of EPR Spectra of Liquid Crystals with Doped Spin Probes from Fully Atomistic Molecular Dynamics Simulations: Exploring Molecular Order and Dynamics at the Phase Transition
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DOI：
10.1002/chem.201001439
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发表时间：
2010-01-01
影响因子：
4.3
通讯作者：
Oganesyan, Vasily S.
中科院分区：
文献类型：
--
作者：
Kuprusevicius, Egidisus;Edge, Ruth;Oganesyan, Vasily S.
分子动力学（MD）模拟正在成为在原子尺度上模拟复杂分子系统以及了解软物质[1]特别是液晶的各种化学、物理和光谱特性的重要工具。[2-4]原子模拟越来越具有预测能力，并可以指导新型功能材料的设计。在这方面，重要的是测试MD预测对现有的实验方法，如先进的光谱技术。近年来，氮氧自由基自旋标记物作为电子顺磁共振（EPR）谱的顺磁探针已获得广泛的应用。[5]带有自旋探针（SP）的EPR被广泛用于测试许多复杂分子系统的结构性质和分子流动性，例如蛋白质和蛋白质-蛋白质复合物、DNA/RNA、聚合物、脂质、固体膜、纳米结构以及液晶（LC）。[6]氮氧自旋探针可以很容易地引入到LC中，以探测不同相中介晶的顺序和动力学。[4，7]方案1显示了通常用于棒状（棒状）LC的硝基氧化物SP的实例。氮氧自由基在化学上相对稳定，并且具有由几乎各向同性的g张量（gxx= 2.0088，gyy= 2.0061，gzz= 2.0027）[4]和各向异性的hy组成的EPR光谱。
Molecular dynamics (MD) simulations are becoming an important tool for modelling complex molecular systems at the atomistic scale and for understanding the various chemical, physical and spectroscopic properties of soft matter [1] and liquid crystals in particular.[2–4] Increasingly, atomistic simulations have predictive power and can guide the design of novel functional materials. In this respect it is important to test MD predictions against available experimental methods, such as advanced spectroscopic techniques. Recently, the use of nitroxide spin labels as paramagnetic probes for electron paramagnetic resonance (EPR) spectroscopy has attained wide applicability.[5] EPR with spin probes (SP) is widely used to test structural properties and molecular mobility of numerous complex molecular systems, such as proteins and protein–protein complexes, DNA/RNA, polymers, lipids, solid films, nanostructures and also liquid crystals (LC).[6]Nitroxide spin probes can be readily introduced into LCs to probe the order and dynamics of mesogens in different phases.[4, 7] Scheme 1 shows an example of a cholesteric nitroxide SP typically used for calamitic (rod-shaped) LCs. The nitroxide radical is chemically relatively stable and has an EPR spectrum consisting of an almost isotropic g tensor (gxx= 2.0088, gyy= 2.0061, gzz= 2.0027)[4] with anisotropic hy-