Surface adsorption and hopping cause probe-size-dependent microrheology of actin networks
Surface adsorption and hopping cause probe-size-dependent microrheology of actin networks
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DOI：
10.1103/physreve.83.041902
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发表时间：
2011-04-07
影响因子：
2.4
通讯作者：
Tang, Jay X.
中科院分区：
文献类型：
--
作者：
He, Jun;Tang, Jay X.
主要由丰富的细胞骨架蛋白肌动蛋白形成的细丝网络赋予动物细胞其形状和弹性。通过跟踪嵌入在网络中的微米尺寸的探针珠，研究了重组肌动蛋白网络的流变性。我们通过改变探针颗粒表面的粘性来研究微观流变学是如何依赖于它们的表面性质的。为此，我们选择了羧酸盐聚苯乙烯(PS)小球、硅胶小球、牛血清白蛋白(BSA)包覆的PS小球和聚乙二醇(PEG)接枝的PS小球，通过共聚焦成像和微观流变学表征，这些小球对肌动蛋白细丝表现出下降的粘性。对于所有四种类型的珠子，都观察到了探针大小与微观流变学的关系。对于光滑的聚乙二醇珠，颗粒跟踪微观流变学使用较小的珠子检测到较弱的网络，这些珠子往往通过从一个限制“笼子”跳到另一个限制“笼子”来扩散通过网络。对于其他三种类型的珠子来说，这一趋势正好相反，对于这些类型的珠子，微观流变学测量到较小的珠子由于附近的细丝物理吸附到珠子表面而形成更坚硬的网络。我们用两个简单的模型解释了探针大小的依赖关系。我们还利用定量图像分析评估了非吸附微珠表面附近的耗尽效应，并讨论了耗尽对微观流变学的可能影响。为了准确地确定肌动蛋白网络在体外和体内的流变学，有必要对这些影响进行分析。
A network of filaments formed primarily by the abundant cytoskeletal protein actin gives animal cells their shape and elasticity. The rheological properties of reconstituted actin networks have been studied by tracking micron-sized probe beads embedded within the networks. We investigate how microrheology depends on surface properties of probe particles by varying the stickiness of their surface. For this purpose, we chose carboxylate polystyrene (PS) beads, silica beads, bovine serum albumin (BSA)-coated PS beads, and polyethylene glycol (PEG)-grafted PS beads, which show descending stickiness to actin filaments, characterized by confocal imaging and microrheology. Probe size dependence of microrheology is observed for all four types of beads. For the slippery PEG beads, particle-tracking microrheology detects weaker networks using smaller beads, which tend to diffuse through the network by hopping from one confinement "cage" to another. This trend is reversed for the other three types of beads, for which microrheology measures stiffer networks for smaller beads due to physisorption of nearby filaments to the bead surface. We explain the probe size dependence with two simple models. We also evaluate depletion effect near nonadsorption bead surface using quantitative image analysis and discuss the possible impact of depletion on microrheology. Analysis of these effects is necessary in order to accurately define the actin network rheology both in vitro and in vivo.