A general model for nuclear magnetic resonance (NMR) relaxation studies of fluid bilayer systems is introduced, combining a mesoscopic Brownian dynamics description of the bilayer with atomistic molecular dynamics (MD) simulations. An example is given for dipalmitoylphosphatidylcholine in 2H2O solvent and compared with the experiment. Experimental agreement is within a factor of 2 in the water relaxation rates, based on a postulated model with fixed parameters, which are largely available from the MD simulation. Relaxation rates are particularly sensitive to the translational diffusion of water perturbed by the interface dynamics and structure. Simulation results suggest that a notable deviation in the relaxation rates may follow from the commonly used small-angle approximation of bilayer undulation. The method has the potential to overcome the temporal and spatial limitations in computing NMR relaxation with atomistic MD, as well as the shortcomings of continuum models enabling a consistent description of experiments performed on a solvent lipid and added spin probes. This work opens for possibilities to understand relaxation processes involving systems such as micelles, multilamellar vesicles, red blood cells, and so forth at biologically relevant timescales in great detail.

中文翻译：

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柔性表面上的布朗平移动力学：流体膜相的核自旋弛豫。

介绍了流体双层系统的核磁共振（NMR）弛豫研究的通用模型，将双层的介观布朗动力学描述与原子分子动力学（MD）模拟相结合。给出了在2H2O溶剂中的二棕榈酰磷脂酰胆碱的实例，并与实验进行了比较。基于具有固定参数的假定模型，实验一致性在水松弛率的2倍之内，而该模型可从MD模拟中获得。弛豫速率对受界面动力学和结构扰动的水的平移扩散特别敏感。仿真结果表明，松弛率的显着偏差可能来自双层波纹的常用小角度近似。该方法有可能克服用原子MD进行NMR弛豫计算时在时间和空间上的局限性，以及连续谱模型的缺点，从而无法对在溶剂脂质和添加的自旋探针上进行的实验进行一致的描述。这项工作为在生物学相关的时间尺度上更详细地理解包括胶束，多层囊泡，红细胞等系统的放松过程提供了可能性。