Strange kinetics of bulk-mediated diffusion on lipid bilayers.
Strange kinetics of bulk-mediated diffusion on lipid bilayers.
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DOI：
10.1039/c6cp00937a
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发表时间：
2016-05-14
期刊：
影响因子：
--
通讯作者：
Peersen OB
中科院分区：
文献类型：
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作者：
Krapf D;Campagnola G;Nepal K;Peersen OB
固液界面扩散在许多技术和生物物理过程中至关重要。虽然它的行为看起来很简单，但最近的研究表明，被动超扩散运输表明表面上的扩散可能隐藏着丰富的复杂性。特别地，当分子从表面瞬时释放以执行三维偏移进入液体本体时，发生本体介导的扩散。这种现象具有二分法，其中分子总是返回到表面，但平均跳跃长度是无限的。这样的行为与中心极限定理的崩溃和弱遍历性破缺有关。在这里，我们使用单粒子跟踪研究支持的脂质双层上的批量介导的扩散的统计。我们发现，时间平均的均方位移（MSD）的个人轨迹，原型措施在扩散过程中，不收敛到合奏MSD，但它仍然是一个随机变量，即使在很长的观测时间限制。时间平均值的分布与Lévy飞行模型一致。我们的研究结果还揭示了位移统计中有趣的异常现象。时间平均的MSD依赖于实验时间，分数阶矩的研究表明，|r（t）|q <$$> tqv（q）具有非线性指数，即v（q）<$const。这种类型的行为被称为强反常扩散，在实验观察中很少见。
Diffusion at solid-liquid interfaces is crucial in many technological and biophysical processes. Although its behavior seems deceivingly simple, recent studies showing passive superdiffusive transport suggest diffusion on surfaces may hide rich complexities. In particular, bulk-mediated diffusion occurs when molecules are transiently released from the surface to perform three-dimensional excursions into the liquid bulk. This phenomenon bears the dichotomy where a molecule always return to the surface but the mean jump length is infinite. Such behavior is associated with a breakdown of the central limit theorem and weak ergodicity breaking. Here, we use single-particle tracking to study the statistics of bulk-mediated diffusion on a supported lipid bilayer. We find that the time-averaged mean square displacement (MSD) of individual trajectories, the archetypal measure in diffusion processes, does not converge to the ensemble MSD but it remains a random variable, even in the long observation-time limit. The distribution of time averages is shown to agree with a Lévy flight model. Our results also unravel intriguing anomalies in the statistics of displacements. The time averaged MSD is shown to depend on experimental time and investigations of fractional moments show a scaling 〈|r(t)|q〉 ∼ tqv(q) with non-linear exponents, i.e. v(q) ≠ const. This type of behavior is termed strong anomalous diffusion and is rare among experimental observations.