F-actin, a model polymer for semiflexible chains in dilute, semidilute, and liquid crystalline solutions
F-actin, a model polymer for semiflexible chains in dilute, semidilute, and liquid crystalline solutions
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DOI：
10.1016/s0006-3495(96)79630-3
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发表时间：
1996-02-01
影响因子：
3.4
通讯作者：
Janmey, PA
中科院分区：
文献类型：
--
作者：
Kas, J;Strey, H;Janmey, PA
单个肌动蛋白丝进行了分析，从稀释（0.2微克/毫升），其中长丝只与溶剂相互作用，浓度（4.0毫克/毫升），在F-肌动蛋白形成一个反相的溶液。持续长度近似于1.8 μ m，平均长度近似于22 μ m（Kaufmann等人，1992）确定肌动蛋白作为研究半柔性聚合物动力学的模型。在稀溶液中，除了扩散运动外，细丝还表现出热弯曲波动。在较高的半稀释浓度（1.4毫克/毫升）的三维重建的共聚焦图像的荧光标记的细丝在矩阵中的未标记的F-肌动蛋白揭示细丝之间的空间相互作用，占这些解决方案的粘弹性行为。这些标记链的限制性波动揭示了由周围的肌动蛋白围绕细丝形成的虚拟管。平均管直径[a]与单体浓度c成比例，[a]与c-（（0.5 +/-0.15））成比例。在半稀释溶液（c =（0.1-2.0）mg/ml）中，细丝的扩散主要是沿着细丝轮廓扩散（爬行），很少通过重塑周围细丝来释放束缚。对于半稀溶液，平行于沿着管的自扩散系数D随链长线性减小。对于浓度>2.5 mg/ml，发生从各向同性缠结相到各向同性和双相畴之间共存的转变。细丝的分子运动的分析表明，在对齐的域中的细丝处于热平衡，并且平行于指向矢D-平行于的扩散系数几乎与细丝长度无关。我们还报告了新的直接观察u形缺陷，称为发夹，在dielectric域。
Single actin filaments were analyzed in solutions ranging from dilute (0.2 mu g/ml), where filaments interact only with solvent, to concentrations (4.0 mg/ml) at which F-actin forms a nematic phase. A persistence length of similar to 1.8 mu m and an average length of similar to 22 mu m (Kaufmann et al., 1992) identify actin as a model for studying the dynamics of semiflexible polymers. In dilute solutions the filaments exhibit thermal bending undulations in addition to diffusive motion. At higher semidilute concentrations (1.4 mg/ml) three-dimensional reconstructions of confocal images of fluorescently labeled filaments in a matrix of unlabeled F-actin reveal steric interactions between filaments, which account for the viscoelastic behavior of these solutions. The restricted undulations of these labeled chains reveal the virtual tube formed around a filament by the surrounding actin. The average tube diameter [a] scales with monomer concentration c as [a] proportional to c-((0.5 +/- 0.15)). The diffusion of filaments in semidilute solutions (c = (0.1-2.0) mg/ml) is dominated by diffusion along the filament contour (reptation), and constraint release by remodeling of the surrounding filaments is rare. The self-diffusion coefficient D-parallel to along the tube decreases linearly with the chain length for semidilute solutions. For concentrations >2.5 mg/ml a transition occurs from an isotropic entangled phase to a coexistence between isotropic and nematic domains. Analysis of the molecular motions of filaments suggests that the filaments in the aligned domains are in thermal equilibrium and that the diffusion coefficient parallel to the director D-parallel to is nearly independent of filament length. We also report the novel direct observation of u-shaped defects, called hairpins, in the nematic domains.