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Bridging the gap between Molecular Dynamics and EPR spectroscopy: Application to Liquid Crystal systems

弥合分子动力学和 EPR 光谱之间的差距：在液晶系统中的应用

基本信息

批准号：
EP/H020411/1
负责人：
Vasily Oganesyan
金额：
$ 36.53万
依托单位：
University of East Anglia
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH020411%2F1
关键词：
Bridging gap between Molecular Dynamics

项目摘要

Liquid crystals (LCs) are an intermediate state of matter that combines both long range order, as found in crystals, and disorder, a characteristic of fluids. This combination of properties gives rise to unique optical and electrical properties that allow LCs to be switched rapidly by electric fields. These properties underlay their widespread application, for example, in displays as seen in flat TV screens and digital watches. The ordering of molecules in LC phases can be, for example, as parallel rods (termed nematic) or as stacks of discs (termed columnar discotics). The latter can conduct charge up and down the columns. This offers potential applications as organic electronic charge transport materials in devices such as light emitting diodes (LEDs), one-dimensional conductors, to provide new types of photoconductors, and photovoltaic solar cells. The underlying molecular organisation must be engineered to produce electron-hole recombination for luminescence or separation for solar cells. Molecular organisation can be by vacuum deposition or the formation of films. The growing demand for LCs with new properties is leading to the development of new mixtures of liquid crystals, new ways to align LC layers for holographic video projection, and the production of new polymeric liquid crystals. The exploitation of self-organising LCs is an important avenue of current research. In order to design novel materials with desired properties it is necessary to describe and predict their behaviour from the molecular level. Recently, major advances in both theoretical and experimental areas have emerged which promise progress in the studies of complex partially ordered molecular systems such as LCs. Firstly, spin labels, specially designed chemical agents that carry a stable unpaired electron, can be introduced within complex molecular systems in order to report on the order and dynamics of surrounding molecules. Because an electron has a magnetic moment it can interact with an external magnetic field. Electron Paramagnetic Resonance (EPR) measures this interaction in the form of spectral line shape. The orientation of the spin label to the magnetic field has a dramatic effect on this line shape and therefore molecular mobility, dynamics and distribution can be studied. EPR is a technique that acts as a snapshot of very fast molecular motions and can resolve molecular re-orientational dynamics of the introduced spin probe over times shorter than a billionth of a second. Recent advances in EPR instrumentation, using different frequencies with spin labels and probes has become an important method for studying structure and dynamics of complex phases such as LCs, of proteins and their complexes, DNA/RNA, polymers, lipids and nanostructures. Secondly, the huge increase in computer power over the last decade has led to an increase in the use of molecular dynamics (MD) simulations as a tool to understand complex chemical systems with the potential to predict various properties of complex self-organising systems such as LCs, LC mixtures and composite systems. Yet there is no general methodology and user-friendly computational tools which are able to link directly state-of-the art MD simulations of complex molecular systems with the simulation and analysis of EPR spectra.The aim of this proposal is to bridge the gap between MD simulations and EPR spectroscopy and to develop methodology, which would enable one to obtain a detailed description and reach unambiguous conclusions about molecular arrangement and interactions within complex molecular systems. In the proposed work, this methodology will be applied to different types of LCs, mixtures and hybrid systems. The output of this proposal will be available to the international scientific community in the form of user-friendly software.

液晶（LC）是物质的一种中间状态，它结合了晶体中的长程有序和流体的无序特性。这种性质的组合产生了独特的光学和电学性质，允许LC通过电场快速切换。这些性质使得它们广泛应用于例如平板电视屏幕和数字手表中的显示器。LC相中的分子的排序可以是例如平行杆（称为平行杆）或盘的堆叠（称为柱状盘）。后者可以在柱子上上下传导电荷。这提供了作为有机电子电荷传输材料在诸如发光二极管（LED）、一维导体等器件中的潜在应用，以提供新型光电导体和光伏太阳能电池。必须设计潜在的分子组织以产生用于太阳能电池的发光或分离的电子-空穴复合。分子组织可以通过真空沉积或膜的形成。对具有新特性的LC的需求不断增长，导致开发新的液晶混合物、用于全息视频投影的LC层对准的新方法以及新的聚合物液晶的生产。自组织液晶的开发是当前研究的一个重要方向。为了设计具有所需性能的新型材料，有必要从分子水平描述和预测它们的行为。近年来，在理论和实验两个方面都取得了重大进展，这为复杂的部分有序分子系统（如液晶）的研究带来了希望。首先，自旋标记，特别设计的化学试剂，携带一个稳定的未配对电子，可以引入复杂的分子系统，以报告周围分子的顺序和动力学。因为电子具有磁矩，所以它可以与外部磁场相互作用。电子顺磁共振（EPR）以谱线形状的形式测量这种相互作用。自旋标记对磁场的取向对这种线形有显著的影响，因此可以研究分子的迁移率、动力学和分布。EPR是一种作为非常快的分子运动的快照的技术，并且可以在短于十亿分之一秒的时间内解析引入的自旋探针的分子重新取向动力学。EPR仪器的最新进展，使用不同的频率与自旋标签和探针已成为一个重要的方法，用于研究复杂的相，如LC，蛋白质及其复合物，DNA/RNA，聚合物，脂质和纳米结构的结构和动力学。其次，在过去的十年中，计算机能力的巨大增长导致了分子动力学（MD）模拟作为理解复杂化学系统的工具的使用增加，该工具具有预测复杂自组织系统（如LC，LC混合物和复合系统）的各种特性的潜力。目前还没有通用的方法和用户友好的计算工具能够将复杂分子体系的最先进的分子动力学模拟与EPR谱的模拟和分析直接联系起来。本提案的目的是弥合分子动力学模拟与EPR谱之间的差距，并发展方法学，这将使人们能够获得详细的描述并得出关于复杂分子系统内的分子排列和相互作用的明确结论。在拟议的工作中，这种方法将适用于不同类型的LC，混合物和混合系统。这项建议的产出将以方便用户的软件形式提供给国际科学界。