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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Influence of the Shape of Crowding Particles on the Structural Transitions in a Polymer
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Influence of the Shape of Crowding Particles on the Structural Transitions in a Polymer

机译：拥挤颗粒形状对聚合物结构转变的影响

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摘要

We investigate the structural transitions in a polymer induced by spherical and nonspherical crowding particles over a wide range of conditions. The polymer conformations are specified by the radius of gyration and the quality of the solvent in the absence of crowding particles. In the presence of crowding particles, the structures are altered by the volume fraction, size, shape, and polydispersity of the crowders. We show that crowding induces an array of structural changes, ranging from helix, helical hairpin (HH), and multiple helix bundles (HBs), depending on the interplay of multiple length and energy scales including the solvent quality, length of the polymer, temperature, and the characteristics of the crowding agents. In nearly good solvents, the polymer undergoes coil—helix transition in accord with the predictions based on the entropic stabilization mechanism. Higher-order (HH and HB) structures are obtained in poor or moderately poor solvents. In a binary mixture of spherical crowders, the effect of the two components is largely additive with the polymer undergoing greater compaction at higher volume fraction. In contrast to spherical crowders, spherocylinder-like crowders have a dramatically different effect on the diagram of states of the polymer. In the presence of spherocylinders, the polymer prefers to form a nearly ideal helix, especially at low temperatures and high aspect ratios of the crowders, at volume fractions that are not large enough for nematic order. Surprisingly, there is a complete absence of HH and HB in the range of conditions explored here. The dominant formation of spherocylinder-induced helix formation is due to the tendency of the spherocylinders and the polymer to align along the director formed by an increase in nematic order only in the vicinity of the polymer. Our study, which has produced several testable predictions, shows that only by probing the effects of crowding on a polymer (or a protein and RNA) over a wide range of conditions can the diagram of states be quantitatively described.
机译：我们研究了在各种条件下球形和非球形的拥挤颗粒在聚合物中引起的结构转变。聚合物的构象由回转半径和在没有拥挤颗粒的情况下的溶剂质量决定。在拥挤粒子的存在下，结构会因拥挤物的体积分数，大小，形状和多分散性而改变。我们显示拥挤会引起一系列结构变化，范围从螺旋，螺旋发夹（HH）和多个螺旋束（HBs）决定，这取决于多个长度和能量尺度的相互作用，包括溶剂质量，聚合物长度，温度，以及拥挤代理的特征。在接近良好的溶剂中，聚合物会根据基于熵稳定机理的预测经历盘旋-螺旋转变。在不良或中度不良的溶剂中可获得更高阶的（HH和HB）结构。在球形拥挤物的二元混合物中，两种成分的作用在很大程度上相加，而聚合物在更高的体积分数下会经历更大的压实。与球形拥挤器相反，类球形气缸的拥挤器对聚合物的状态图有显着不同的影响。在存在球柱体的情况下，聚合物更倾向于形成近乎理想的螺旋，特别是在低温和高拥挤比的拥挤剂中，其体积分数不足以形成向列顺序。令人惊讶的是，在这里探索的条件范围内，HH和HB完全不存在。球柱体诱导的螺旋形成的主要形成是由于球柱体和聚合物趋向于仅通过在聚合物附近沿向列顺序增加而形成的指向矢排列。我们的研究产生了一些可检验的预测，结果表明，只有在广泛的条件下研究拥挤对聚合物（或蛋白质和RNA）的影响后，状态图才能得到定量描述。

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