Predicting frequency dependent cross-relaxation rates from Molecular Dynamics simulations to provide a basis for a reliable interpretation of experimental NOE data

关于离子液体(ILS)的详细结构和动力学仍存在很大程度的不确定性。特别是，这些液体是如何在分子水平上根据分子间原子-原子接触来组织的。有人认为，特定的分子间相互作用很重要，因此可以用来调节ILS的性质。要解决这些问题，有必要对ILS的详细分子间结构和动力学有一个深刻的了解。最充分地利用核Overhauser效应可能有助于为这些分子细节提供这样的结构和动力学图像。然而，整齐的离子液体的情况与例如大球状蛋白质的情况有很大的不同。在ILS中，构象多样性很大，相遇构型的寿命通常很短，必须考虑平移扩散和重定向动力学中的非理想性。此外，还必须考虑离子液体的特殊纳米结构，这种结构是由正/负离子交替电荷模式施加的。基于扩散的公式是为简单液体开发的，不能假定它是足够的。我们建议用分子动力学方法模拟具有不同反离子的咪唑基离子液体的真实全原子模型，以充分描述特定有意义的自旋组合与频率相关的交叉弛豫现象。温度变化将被用来更好地描述和剖析分子内和分子间弛豫过程的结构和动力学方面的影响。此外，添加分子，如氯仿，将被用来研究这些添加剂与阴离子或阳离子可能的优先相互作用。我们的目标是为我们的合作者拉尔夫·吉尔诺斯在SPP内对实验确定的NOE进行的解释奠定可靠的基础。此外，模拟还将有助于建议和设计未来的核磁共振实验，例如改变同位素组成，以验证和测试模拟结果。

There is still a large degree of uncertainty about the detailed structure and dynamics of ionic liquids (ILs). In particular, how those liquids are organized at the molecular level in terms of intermolecular atom-atom contacts. It has been argued that specific intermolecular interactions matter, and thus might be employed for tuning properties of ILs. To resolve those issues, it is essential to have a profound understanding of the detailed intermolecular structure and dynamics of ILs. Exploiting the Nuclear Overhauser Effect to the fullest could be instrumental in providing such a structural and dynamical picture for those molecular details. However, the situation for a neat ionic liquids is substantially different than for example for the case of large globular proteins. In ILs the conformational diversity is large, the lifetimes of encounter-configurations are typically short, and nonidealities in translatoric diffusion and reorientational dynamics have to be taken into account. Moreover, the specific nanoscale structure of ILs, imposed by the alternating cation/anion charge pattern has to be considered. Diffusion based formulae, developed for simple liquids, cannot be assumed to be adequate. We propose to use molecular dynamics simulations of realistic all atom models of imidazolium based ionic liquids with different counter ions, to fully characterize the frequency dependent cross-relaxation phenomena for particular meaningful spin-combinations. Temperature variation will be used to better characterize and dissect the influence of the structural and dynamical aspects of the intra- and inter-molecular relaxation processes. Moreover, the addition of molecules, such as chloroform, will be used to study the possible preferential interactions of those additives with anions or cations. Our aim is to lay a reliable foundation for the interpretation of experimentally determined NOEs carried out by our collaborator Ralf Giernoth within the SPP. In addition, the simulations will also help to suggest and design future NMR experiments of e.g.varying isotopic composition to verify and test the simulation results.