Slow filament dynamics and viscoelasticity in entangled and active actin networks
Slow filament dynamics and viscoelasticity in entangled and active actin networks
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DOI：
10.1098/rsta.2002.1158
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发表时间：
2003-04-15
期刊：
影响因子：
5
通讯作者：
Sackmann, E
中科院分区：
文献类型：
--
作者：
Keller, M;Tharmann, R;Sackmann, E
本文研究了缠结肌动蛋白网络的粘弹性阻抗与单丝的慢构象动力学和扩散运动之间的关系。通过分析附着胶珠的布朗运动，将单丝动力学可视化并进行分析，从而可以独立测量诸如纠缠和重复时间等特征粘弹性响应时间。我们进一步通过磁镊子微流变仪研究了活性肌动蛋白-重肌球蛋白II网络的频率相关粘弹性阻抗，以深入了解这种高动态和产生力的交联剂（显示出小于1秒的键寿命）对流变性能的影响。我们表明，在高频（高于1hz）下，粘弹性损失模量相对于纠缠网络略有增加（与机械激励期间耗散的能量增加有关），而在低频下，由于网络的交联和终端状态的抑制，阻抗谱的平台变得更加明显。我们的数据提供了证据，表明肌凝蛋白运动蛋白可能作为肌动蛋白皮层的软化剂发挥作用，使细胞屈服应力的适应性降低，从而促进细胞变形。
This paper deals with correlations between the viscoelastic impedance of entangled actin networks and the slow conformational dynamics and diffusive motions of single filaments. The single filament dynamics is visualized and analysed by analysing the Brownian motion of attached colloidal beads, which enables independent measurements of characteristic viscoelastic response times such as the entanglement and reptation times. We further studied the frequency-dependent viscoelastic impedance of active actin-heavy-meromyosin II networks by magnetic-tweezers microrheometry to gain insight into the effect of such highly dynamic and force-generating cross-linkers (exhibiting bond lifetimes of less than 1 s) on the rheological properties. We show that at high frequencies (higher than 1 Hz) the viscoelastic loss modulus is slightly increased relative to the entangled network (associated with an increase in the energy dissipated during mechanical excitations), while at low frequencies the plateau of the impedance spectrum becomes more pronounced as a consequence of the cross-linking of the network and the suppression of the terminal regime. Our data provide evidence that the myosin motor protein may play a role as softener of the actin cortex, enabling the adaptive reduction of the yield stress of cells and thus facilitating cellular deformations.