Buckling-induced zebra stripe patterns in nematic F-actin
Buckling-induced zebra stripe patterns in nematic F-actin
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DOI：
10.1103/physreve.79.031916
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发表时间：
2009-03-01
影响因子：
2.4
通讯作者：
Kaes, Josef
中科院分区：
文献类型：
--
作者：
Gentry, Brian;Smith, David;Kaes, Josef
而不是形成一个简单和均匀的向列液晶，半柔性聚合物的浓缩溶液，如f -肌动蛋白，已经被观察到显示空间周期性的向列指向器开关。当用偏振显微镜观察时，这些图案呈现为交替的明暗带，通常被称为斑马条纹图案。斑马条纹图案，虽然没有完全表征，是由于在向列顺序的周期性方向扭曲。我们通过结合使用两种技术来描述这种模式。利用偏振显微镜，我们量化了周期性取向畸变，并表明在条纹域中，序参量的大小也是周期性变化的。当使用荧光标记的细丝作为标记时，可以看到跨越条纹结构域的细丝经历大角度弯曲。在荧光中，相邻条纹之间也观察到明显的密度差异，密度较小的区域对应于强烈弯曲的细丝。通过直接比较偏振和荧光技术的图案区域，我们发现取向、有序参数、灯丝弯曲和密度的周期性变化是相关的。我们提出，这些影响源于取向和密度的耦合，这种耦合发生在受剪切流动影响的长半柔性聚合物的高浓度溶液中，如先前提出的[P. 6]。de Gennes, Mol. crystal。结晶的液体。(费拉。Pa)。34,177(1977)]。在剪切停止后，强的纤维间相互作用和高压缩性会导致纤维在流动过程中松弛而产生周期性屈曲。这里提出的斑马条纹图案的特征提供了证据，证明在受限的f -肌动蛋白向列线中屈曲产生强烈的周期性弯曲，这是观察到的特征的原因。
Rather than forming a simple and uniform nematic liquid crystal, concentrated solutions of semiflexible polymers, such as F-actin, have been observed to display a spatially periodic switching of the nematic director. When observed with polarization microscopy, these patterns appear as alternating light and dark bands, often referred to as zebra stripe patterns. Zebra stripe patterns, although not fully characterized, are due to periodic orientation distortions in the nematic order. We characterize such patterns by using a combination of two techniques. Using polarization microscopy, we quantify the periodic orientation distortions and show that the magnitude of the order parameter also varies periodically in the striped domains. When using fluorescently labeled filaments as markers, filaments spanning the striped domains are seen to undergo large angle bends. With fluorescence, clear density differences between adjacent stripes are also observed with domains of lesser density corresponding to strongly bent filaments. By directly comparing patterned areas with both polarization and fluorescence techniques, we show that periodic variation in the orientation, order parameter, filament bending, and density are correlated. We propose that these effects originate from the coupling of orientation and density that occurs for highly concentrated solutions of long semiflexible polymers subject to shear flows, as previously proposed [P. de Gennes, Mol. Cryst. Liq. Cryst. (Phila. Pa.) 34, 177 (1977)]. After cessation of shearing, strong interfilament interactions and high compressibility can lead to periodic buckling from the relaxation of filaments stretched during flows. The characterization of zebra stripe patterns presented here provides evidence that buckling in confined F-actin nematics produces strong periodic bending that is responsible for the observed features.