Trajectories of endosomes inside living eukaryotic cells are highly heterogeneous in space and time and diffuse anomalously due to a combination of viscoelasticity, caging, aggregation and active transport. Some of the trajectories display switching between persistent and anti-persistent motion, while others jiggle around in one position for the whole measurement time. By splitting the ensemble of endosome trajectories into slow moving subdiffusive and fast moving superdiffusive endosomes, we analyzed them separately. The mean squared displacements and velocity auto-correlation functions confirm the effectiveness of the splitting methods. Applying the local analysis, we show that both ensembles are characterized by a spectrum of local anomalous exponents and local generalized diffusion coefficients. Slow and fast endosomes have exponential distributions of local anomalous exponents and power law distributions of generalized diffusion coefficients. This suggests that heterogeneous fractional Brownian motion is an appropriate model for both fast and slow moving endosomes. This article is part of a Special Issue entitled: “Recent Advances In Single-Particle Tracking: Experiment and Analysis” edited by Janusz Szwabiński and Aleksander Weron.

中文翻译：

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异质细胞内运输的局部分析：慢速和快速移动的内体

活真核细胞内内体的轨迹在空间和时间上是高度异质的，并且由于粘弹性、笼罩、聚集和主动运输的组合而异常扩散。一些轨迹显示持续运动和反持续运动之间的切换，而其他轨迹则在整个测量时间内在一个位置摇晃。通过将内体轨迹的集合分成缓慢移动的亚扩散和快速移动的超扩散内体，我们分别分析了它们。均方位移和速度自相关函数证实了分裂方法的有效性。应用局部分析，我们表明两个系综都具有局部异常指数和局部广义扩散系数的特征。慢和快内体具有局部异常指数的指数分布和广义扩散系数的幂律分布。这表明异质分数布朗运动是快速和慢速移动内体的合适模型。本文是由 Janusz Szwabiński 和 Aleksander Weron 编辑的题为“单粒子跟踪的最新进展：实验和分析”的特刊的一部分。