Quantitation of liquid-crystalline ordering in F-actin solutions.
Quantitation of liquid-crystalline ordering in F-actin solutions.
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DOI：
10.1016/s0006-3495(92)81647-8
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发表时间：
1992-09
影响因子：
3.4
通讯作者：
Chris M. Coppin;Paul C. Leavis
中科院分区：
文献类型：
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作者：
Chris M. Coppin;Paul C. Leavis
肌动蛋白丝（F-肌动蛋白）是细胞形状和运动的重要决定因素。这些功能依赖于大量纤维在细胞质中的位置和方向的集体组织。大部分的取向组织自发地产生通过液晶形成在浓缩的F-肌动蛋白溶液。在研究这种现象，我们发现，纯化的F-肌动蛋白的解决方案进行连续的相变，从各向同性状态的液晶状态，当平均丝长度或肌动蛋白浓度增加到其各自的阈值以上。相图表示的阈值细丝长度和浓度在相变发生时是一致的，预测由弗洛里的理论对解决方案的非相互作用，刚性圆柱体（弗洛里，1956年b）。然而，与基于该模型的其他预测相反，我们没有发现各向同性和各向异性相共存的证据。此外，相变被证明是温度依赖性的，这表明存在取向依赖的丝间相互作用或温度依赖的丝的灵活性。我们开发了一种简单的方法生长不失真的荧光丙烯酰胺标记的F-肌动蛋白液晶，我们推导出一个简单的理论处理，偏振的荧光测量可用于定量，第一次，自发丝排序的程度（α序参数）在这些F-肌动蛋白液晶。这个顺序参数被发现与长丝长度和浓度单调增加。肌动蛋白液晶可以很容易地通过一种被称为“纹理化”的过程而变形。“通过偏光显微镜观察到在没有ATP的情况下持续存在的锯齿状和螺旋状液晶织构。可能的纹理机制进行了讨论。
Actin filaments (F-actin) are important determinants of cellular shape and motility. These functions depend on the collective organization of numerous filaments with respect to both position and orientation in the cytoplasm. Much of the orientational organization arises spontaneously through liquid crystal formation in concentrated F-actin solutions. In studying this phenomenon, we found that solutions of purified F-actin undergo a continuous phase transition, from the isotropic state to a liquid crystalline state, when either the mean filament length or the actin concentration is increased above its respective threshold value. The phase diagram representing the threshold filament lengths and concentrations at which the phase transition occurs is consistent with that predicted by Flory's theory on solutions of noninteracting, rigid cylinders (Flory, 1956b). However, in contrast to other predictions based on this model, we found no evidence for the coexistence of isotropic and anisotropic phases. Furthermore, the phase transition proved to be temperature dependent, which suggests the existence of orientation-dependent interfilament interactions or of a temperature-dependent filament flexibility. We developed a simple method for growing undistorted fluorescent acrylodan-labeled F-actin liquid crystals; and we derived a simple theoretical treatment by which polarization-of-fluorescence measurements could be used to quantitate, for the first time, the degree of spontaneous filament ordering (nematic order parameter) in these F-actin liquid crystals. This order parameter was found to increase monotonically with both filament length and concentration. Actin liquid crystals can readily become distorted by a process known as "texturing." Zigzaging and helicoidal liquid crystalline textures which persisted in the absence of ATP were observed through the polarizing microscope. Possible texturing mechanisms are discussed.