A biological interpretation of transient anomalous subdiffusion. I. Qualitative model
A biological interpretation of transient anomalous subdiffusion. I. Qualitative model
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DOI：
10.1529/biophysj.106.092619
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发表时间：
2007-02-15
影响因子：
3.4
通讯作者：
Saxton, Michael J.
中科院分区：
文献类型：
--
作者：
Saxton, Michael J.
据报道，质膜中的二维扩散和细胞核和细胞质中的三维扩散存在异常亚扩散。如果一个粒子在一个合适的无限层次的结合位点扩散，扩散是众所周知的，在任何时候都是反常的。但如果层次是有限的，扩散在短时间内是反常的，在长时间内是正常的。对于一组规定的结合位点，蒙特卡罗计算产生的异常扩散指数和扩散是异常的平均时间。如果即使是一个单一的结合位点是存在的，有一个非常短的，几乎是人为的，异常subdiffusion期间，但层次结构的结合位点大大扩展了异常制度。众所周知，由于结合导致的异常亚扩散的基本要求是扩散粒子不能与结合位点处于热平衡;平衡的粒子在任何时候都正常扩散。异常亚扩散由于障碍，然而，仍然发生在热平衡，和异常亚扩散由于结合位点和障碍的组合减少，但不消除平衡。这个物理模型被直接转化为一个可信的生物模型，可以通过单粒子跟踪进行测试。
Anomalous subdiffusion has been reported for two-dimensional diffusion in the plasma membrane and three-dimensional diffusion in the nucleus and cytoplasm. If a particle diffuses in a suitable infinite hierarchy of binding sites, diffusion is well known to be anomalous at all times. But if the hierarchy is finite, diffusion is anomalous at short times and normal at long times. For a prescribed set of binding sites, Monte Carlo calculations yield the anomalous diffusion exponent and the average time over which diffusion is anomalous. If even a single binding site is present, there is a very short, almost artifactual, period of anomalous subdiffusion, but a hierarchy of binding sites extends the anomalous regime considerably. As is well known, an essential requirement for anomalous subdiffusion due to binding is that the diffusing particle cannot be in thermal equilibrium with the binding sites; an equilibrated particle diffuses normally at all times. Anomalous subdiffusion due to barriers, however, still occurs at thermal equilibrium, and anomalous subdiffusion due to a combination of binding sites and barriers is reduced but not eliminated on equilibration. This physical model is translated directly into a plausible biological model testable by single-particle tracking.