Transition from distributional to ergodic behavior in an inhomogeneous diffusion process: Method revealing an unknown surface diffusivity
Transition from distributional to ergodic behavior in an inhomogeneous diffusion process: Method revealing an unknown surface diffusivity
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DOI：
10.1103/physreve.92.022114
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发表时间：
2015-08-10
影响因子：
2.4
通讯作者：
Seki, Kazuhiko
中科院分区：
文献类型：
--
作者：
Akimoto, Takuma;Seki, Kazuhiko
分子在细胞内的扩散通过在膜表面找到靶点，在膜表面提供生物反应方面起着重要作用。目标附近的水滞(缓慢扩散)有助于搜索分子识别目标。在这里，我们考虑了表面扩散系数对有效扩散系数的影响，其中表面扩散比体扩散慢。结果表明，当表面解吸速率有限时，系综平均均方位移随时间呈线性增加，即使在表面上的扩散是反常的(次扩散)的情况下，这也是有效的。此外，表面上的这种缓慢扩散影响了时间平均均方位移(TAMSD)的涨落。我们发现，当测量时间小于特征时间时，TAMSD的起伏仍然很大，并且在相对较大的测量时间内，TAMSD随测量时间的增加而衰减。因此，在目标搜索过程中，我们发现了从非遍历(分布)扩散到遍历扩散的转变。此外，这种涨落分析提供了一种估计未知表面扩散系数的方法。
Diffusion of molecules in cells plays an important role in providing a biological reaction on the surface by finding a target on the membrane surface. The water retardation (slow diffusion) near the target assists the searching molecules to recognize the target. Here, we consider effects of the surface diffusivity on the effective diffusivity, where diffusion on the surface is slower than that in bulk. We show that the ensemble-averaged mean-square displacements increase linearly with time when the desorption rate from the surface is finite, which is valid even when the diffusion on the surface is anomalous (subdiffusion). Moreover, this slow diffusion on the surface affects the fluctuations of the time-averaged mean-square displacements (TAMSDs). We find that fluctuations of the TAMSDs remain large when the measurement time is smaller than a characteristic time, and decays according to an increase of the measurement time for a relatively large measurement time. Therefore, we find a transition from nonergodic (distributional) to ergodic diffusivity in a target search process. Moreover, this fluctuation analysis provides a method to estimate an unknown surface diffusivity.