Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany.
J Chem Phys. 2011 Oct 14;135(14):144118. doi: 10.1063/1.3647875.
Heterogeneous diffusion processes occur in many different fields such as transport in living cells or diffusion in porous media. A characterization of the transport parameters of such processes can be achieved by ensemble-based methods, such as pulsed field gradient nuclear magnetic resonance (PFG NMR), or by trajectory-based methods obtained from single-particle tracking (SPT) experiments. In this paper, we study the general relationship between both methods and its application to heterogeneous systems. We derive analytical expressions for the distribution of diffusivities from SPT and further relate it to NMR spin-echo diffusion attenuation functions. To exemplify the applicability of this approach, we employ a well-established two-region exchange model, which has widely been used in the context of PFG NMR studies of multiphase systems subjected to interphase molecular exchange processes. This type of systems, which can also describe a layered liquid with layer-dependent self-diffusion coefficients, has also recently gained attention in SPT experiments. We reformulate the results of the two-region exchange model in terms of SPT-observables and compare its predictions to that obtained using the exact transformation which we derived.
基于单粒子追踪和脉冲梯度场核磁共振的关联研究
在许多不同的领域中，如活细胞内的物质传输或多孔介质中的扩散，都会发生非均相扩散过程。此类过程的传输参数的特征可以通过基于集合的方法（如脉冲梯度场核磁共振（PFG NMR））或通过单粒子追踪（SPT）实验获得的基于轨迹的方法来实现。在本文中，我们研究了这两种方法之间的一般关系及其在非均相体系中的应用。我们从 SPT 中推导出扩散系数分布的解析表达式，并进一步将其与 NMR 自旋回波扩散衰减函数相关联。为了说明这种方法的适用性，我们采用了一种成熟的两区域交换模型，该模型在多相体系的 PFG NMR 研究中广泛用于相际分子交换过程。这种类型的体系也可以描述具有与层相关的自扩散系数的层状液体，最近在 SPT 实验中也受到了关注。我们根据 SPT 可观测值重新表述了两区域交换模型的结果，并将其预测与我们推导的精确变换的预测进行了比较。
