用荧光相关光谱法分辨时空中的反常输运
Anomalous transport resolved in space and time by fluorescence correlation spectroscopy
摘要：
在拥挤的细胞膜中普遍观察到的是分子运输不遵循菲克扩散，而是呈现亚扩散。这种行为的微观起源还没有被理解和高度辩论。在这里，我们讨论了两个模型的时空动力学的亚扩散：分数布朗运动和受阻运动由于不动的障碍。我们表明，不同的微观机制，可以区分使用荧光相关光谱（FCS）的共聚焦检测区域的系统变化。我们提供了一个空间分辨FCS的理论框架，通过推广FCS理论超越了空间高斯传输的共同假设。我们推导出FCS自相关函数的主公式，从中可以看出，FCS实验的束腰是一个同样重要的参数，散射实验的波数。这些结果导致两个模型的FCS相关性的标度特性，这是在硅片实验测试。此外，我们的缩放预测与Wawrezinieck等人[Biophys. J. 89，4029（2005）]用于跨膜蛋白的体内实验。
英文摘要：
A ubiquitous observation in crowded cell membranes is that molecular transport does not follow Fickian diffusion but exhibits subdiffusion. The microscopic origin of such a behaviour is not understood and highly debated. Here we discuss the spatio-temporal dynamics for two models of subdiffusion: fractional Brownian motion and hindered motion due to immobile obstacles. We show that the different microscopic mechanisms can be distinguished using fluorescence correlation spectroscopy (FCS) by systematic variation of the confocal detection area. We provide a theoretical framework for space-resolved FCS by generalising FCS theory beyond the common assumption of spatially Gaussian transport. We derive a master formula for the FCS autocorrelation function, from which it is evident that the beam waist of an FCS experiment is a similarly important parameter as the wavenumber of scattering experiments. These results lead to scaling properties of the FCS correlation for both models, which are tested by in silico experiments. Further, our scaling prediction is compatible with the FCS half-value times reported by Wawrezinieck et al. [Biophys. J. 89, 4029 (2005)] for in vivo experiments on a transmembrane protein.
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