Into the polymer brush regime through the "grafting-to" method: densely polymer-grafted rodlike viruses with an unusual nematic liquid crystal behavior.
Into the polymer brush regime through the "grafting-to" method: densely polymer-grafted rodlike viruses with an unusual nematic liquid crystal behavior.
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DOI：
10.1039/c5sm02015h
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发表时间：
2016-01
期刊：
影响因子：
3.4
通讯作者：
Tingting Zan;Fengchi Wu;Xiaodong Pei;Shao-yi Jia;Rannan Zhang;Song-hai Wu;Z. Niu;Zhenkun Zhang
中科院分区：
文献类型：
--
作者：
Tingting Zan;Fengchi Wu;Xiaodong Pei;Shao-yi Jia;Rannan Zhang;Song-hai Wu;Z. Niu;Zhenkun Zhang
目前的工作报告了一个有趣的发现，即聚合物刷的强链间排斥力如何施加在丝状病毒等蛋白质复合物上，从而在分子尺度上引起组成亚基的微妙变化。这种变化转化为棒状病毒在三维空间中手性排序的宏观重排。为此，研究人员开发了一种直接的“接枝到”聚乙二醇化方法，将丝状病毒与聚乙二醇（PEG）紧密接枝。接枝密度如此之高，以至于PEG处于聚合物刷状状态，从而产生具有薄病毒骨架的直而粗的棒状颗粒。由于在云母表面的吸附，由于PEG刷的位阻斥力，观察到密集聚乙二醇化的病毒分裂成碎片。PEG的高接枝密度使病毒具有与离子强度无关的各向同性-向列相（I-N）液晶（LC）相变，密集聚乙二醇化的病毒在低得多的病毒浓度下进入向列相LC。最重要的是，完整的病毒和低接枝密度的PEG接枝的病毒可以形成手性向列相LC，而密集的PEG接枝的病毒只能形成纯向列相LC。这可以追溯到由PEG刷的空间排斥驱动的病毒主要外壳蛋白的二级到三级结构变化。由接枝密度或I-N - LC跃迁得到的表征接枝PEG构象的定量参数与理论预测非常吻合。
The current work reports an intriguing discovery of how the force exerted on protein complexes like filamentous viruses by the strong interchain repulsion of polymer brushes can induce subtle changes of the constituent subunits at the molecular scale. Such changes transform into the macroscopic rearrangement of the chiral ordering of the rodlike virus in three dimensions. For this, a straightforward "grafting-to" PEGylation method has been developed to densely graft a filamentous virus with poly(ethylene glycol) (PEG). The grafting density is so high that PEG is in the polymer brush regime, resulting in straight and thick rodlike particles with a thin viral backbone. Scission of the densely PEGylated viruses into fragments was observed due to the steric repulsion of the PEG brush, as facilitated by adsorption onto a mica surface. The high grafting density of PEG endows the virus with an isotropic-nematic (I-N) liquid crystal (LC) phase transition that is independent of the ionic strength and the densely PEGylated viruses enter into the nematic LC phase at much lower virus concentrations. Most importantly, while the intact virus and the one grafted with PEG of low grafting density can form a chiral nematic LC phase, the densely PEGylated viruses only form a pure nematic LC phase. This can be traced back to the secondary to tertiary structural change of the major coat protein of the virus, driven by the steric repulsion of the PEG brush. Quantitative parameters characterising the conformation of the grafted PEG derived from the grafting density or the I-N LC transition are elegantly consistent with the theoretical prediction.