Development of anomalous diffusion among crowding proteins
Development of anomalous diffusion among crowding proteins
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DOI：
10.1039/b924149c
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发表时间：
2010-01-01
期刊：
影响因子：
3.4
通讯作者：
Franosch, Thomas
中科院分区：
文献类型：
--
作者：
Horton, Margaret R.;Hoefling, Felix;Franosch, Thomas
在细胞膜中，蛋白质和脂类在高度拥挤和异质的环境中扩散，蛋白质或脂类的聚集体和致密结构域阻碍了分子的扩散。一般来说，运动受阻会导致异常的运输，尽管这种行为发生的本质仍在争论中，很难通过实验进行调查。在这里，我们提出了一项系统的研究，其中结合到支持脂膜的蛋白质在两个维度上自由扩散，但越来越多地被其他类似蛋白质的存在所阻碍。在我们的模型系统中，通过改变生物素化脂质锚的浓度来很好地控制蛋白质亲和素在脂双层上的表面覆盖率。利用荧光相关光谱(FCS)，我们测量了长时间的时间关联函数，并将其转换为扩散蛋白质的均方位移。我们的方法允许高精度的数据，并明确区分异常扩散和正常扩散。它使我们能够研究异常扩散的开始，当膜蛋白的面积覆盖率增加到大约5%以上时就会发生。这一过渡区表现出明显的空间异质性。随着堆积分数的进一步增加，输运变得越来越反常，表现为次扩散指数的降低。
In cell membranes, proteins and lipids diffuse in a highly crowded and heterogeneous landscape, where aggregates and dense domains of proteins or lipids obstruct the path of diffusing molecules. In general, hindered motion gives rise to anomalous transport, though the nature of the onset of this behavior is still under debate and difficult to investigate experimentally. Here, we present a systematic study where proteins bound to supported lipid membranes diffuse freely in two dimensions, but are increasingly hindered by the presence of other like proteins. In our model system, the surface coverage of the protein avidin on the lipid bilayer is well controlled by varying the concentration of biotinylated lipid anchors. Using fluorescence correlation spectroscopy (FCS), we measure the time correlation function over long times and convert it to the mean-square displacement of the diffusing proteins. Our approach allows for high precision data and a clear distinction between anomalous and normal diffusion. It enables us to investigate the onset of anomalous diffusion, which takes place when the area coverage of membrane proteins increases beyond approximately 5%. This transition region exhibits pronounced spatial heterogeneities. Upon increasing the packing fraction further, transport becomes more and more anomalous, manifested in a decrease of the exponent of subdiffusion.