动态非均匀介质中的扩散限制反应
Diffusion-limited reactions in dynamic heterogeneous media
摘要：
活细胞中的大多数生化反应依赖于在异质的过度拥挤的细胞质介质中扩散搜索靶分子或区域。介质的快速重排不断改变扩散颗粒局部感受到的有效扩散率，从而影响反应事件的首次通过时间的分布。在这里，我们调查这些动态的时空异质性扩散限制反应的效果。我们描述了一个通用的数学框架，将普通均匀布朗运动的许多结果转化为非均匀扩散。特别是，我们推导出反应事件的首次通过时间的概率密度，并展示了动态无序如何扩大分布，并增加了反应目标的短轨迹和长轨迹的可能性。虽然平均而言，无序减慢了反应动力学，但其动态特性有利于更快地搜索和实现由单个分子触发的单个反应事件。
英文摘要：
Most biochemical reactions in living cells rely on diffusive search for target molecules or regions in a heterogeneous overcrowded cytoplasmic medium. Rapid re-arrangements of the medium constantly change the effective diffusivity felt locally by a diffusing particle and thus impact the distribution of the first-passage time to a reaction event. Here, we investigate the effect of these dynamic spatio-temporal heterogeneities onto diffusion-limited reactions. We describe a general mathematical framework to translate many results for ordinary homogeneous Brownian motion to heterogeneous diffusion. In particular, we derive the probability density of the first-passage time to a reaction event and show how the dynamic disorder broadens the distribution and increases the likelihood of both short and long trajectories to reactive targets. While the disorder slows down reaction kinetics on average, its dynamic character is beneficial for a faster search and realization of an individual reaction event triggered by a single molecule.
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