Anomalous diffusion of proteins due to molecular crowding
Anomalous diffusion of proteins due to molecular crowding
复制标题
DOI：
10.1529/biophysj.104.051078
复制
发表时间：
2005-11-01
影响因子：
3.4
通讯作者：
Fradin, C
中科院分区：
文献类型：
--
作者：
Banks, DS;Fradin, C
我们研究了示踪蛋白在高浓度的随机卷曲聚合物和球状蛋白质溶液中的扩散，模拟细胞环境中遇到的拥挤条件。使用荧光相关光谱，我们测量了异常扩散指数α，其表征了示踪蛋白的均方位移对时间的依赖性，< r（2）（t）>类似于t（α）。我们观察到，即使在低障碍物浓度下，浓度高达400 g/l的葡聚糖溶液中的蛋白质扩散也是亚扩散的（α < 1）。反常扩散指数a随障碍物浓度和分子量的增加而连续减小，但不依赖于缓冲离子强度，也不强烈依赖于溶液温度。在非常高的无规卷曲聚合物浓度下，α达到接近3/4的极限值α（1），我们认为这是示踪蛋白和葡聚糖链段的运动之间耦合的特征。一个类似的，虽然不太明显，亚扩散行为观察到的链霉亲和素在浓缩的球状蛋白质溶液中的扩散。这些观察结果表明，在细胞质和细胞核中的蛋白质扩散应该是异常的，以及在细胞中的溶质扩散系数的测量和依赖于扩散的细胞过程的建模的后果。
We have studied the diffusion of tracer proteins in highly concentrated random-coil polymer and globular protein solutions imitating the crowded conditions encountered in cellular environments. Using fluorescence correlation spectroscopy, we measured the anomalous diffusion exponent alpha characterizing the dependence of the mean-square displacement of the tracer proteins on time, < r(2)(t)> similar to t(alpha). We observed that the diffusion of proteins in dextran solutions with concentrations up to 400 g/l is subdiffusive (alpha < 1) even at low obstacle concentration. The anomalous diffusion exponent a decreases continuously with increasing obstacle concentration and molecular weight, but does not depend on buffer ionic strength, and neither does it depend strongly on solution temperature. At very high random-coil polymer concentrations, alpha reaches a limit value of alpha(1) approximate to 3/4, which we take to be the signature of a coupling between the motions of the tracer proteins and the segments of the dextran chains. A similar, although less pronounced, subdiffusive behavior is observed for the diffusion of streptavidin in concentrated globular protein solutions. These observations indicate that protein diffusion in the cell cytoplasm and nucleus should be anomalous as well, with consequences for measurements of solute diffusion coefficients in cells and for the modeling of cellular processes relying on diffusion.