Mechanism of the Temperature-Dependent Self-Assembly and Polymorphism of Chitin,Chemistry of Materials

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Mechanism of the Temperature-Dependent Self-Assembly and Polymorphism of Chitin
Chemistry of Materials ( IF 7.2 ) Pub Date : 2023-08-01 , DOI: 10.1021/acs.chemmater.3c01313
Aarion Romany ₁ , Gregory F. Payne ₂ , Jana Shen ₁

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Chitin is the second most abundant natural biopolymer. Its crystalline structures have been extensively studied. However, the mechanism of chitin’s self-assembly is unknown. Here, we applied all-atom molecular dynamics to study chitin’s self-assembly process at different temperatures. Strikingly, at 278 K, an amorphous aggregate was formed, whereas at 300 K single-sheet and at 323 K both single-sheet and multisheet nanofibril regions were formed. The nanofibrils contain antiparallel, parallel, or mixed orientation chains, with antiparallel being slightly preferred, recapitulating chitin’s polymorphism observed in nature. The inverse temperature dependence is consistent with a recent experiment conducted in the aqueous KOH/urea solution. The analysis suggested that the multisheet nanofibrils are assembled by stacking the single nanofibril sheets, which are formed through two types of pathways in which hydrophobic collapse either precedes or is concomitant with the increasing number of interchain hydrogen bonds and solvent expulsion. Furthermore, the antiparallel and parallel chains are mediated by different interchain hydrogen bonds. The analysis also suggested that the inverse temperature dependence may be attributed to the hydrophobic effect reminiscent of the low critical solution temperature phase behavior. The present study provides a rich, atomic-level view of chitin’s polymorphic self-assembly process, paving the way for the rational design of chitin-derived novel materials.

中文翻译：

甲壳素的温度依赖性自组装和多态性机制

甲壳素是第二丰富的天然生物聚合物。其晶体结构已被广泛研究。然而，甲壳素自组装的机制尚不清楚。在这里，我们应用全原子分子动力学研究甲壳素在不同温度下的自组装过程。引人注目的是，在 278 K 时形成了无定形聚集体，而在 300 K 时形成了单片，在 323 K 时形成了单片和多片纳米原纤维区域。纳米原纤维含有反平行、平行或混合的取向链，其中反平行是稍微优选的，概括了自然界中观察到的几丁质的多态性。逆温度依赖性与最近在 KOH/尿素水溶液中进行的实验一致。分析表明，多片纳米原纤是通过堆叠单个纳米原纤片组装而成的，它们是通过两种类型的途径形成的，其中疏水性崩溃要么先于链间氢键数量的增加，要么同时发生，并伴随着溶剂排出。此外，反平行链和平行链由不同的链间氢键介导。分析还表明，逆温度依赖性可能归因于疏水效应，让人想起低临界溶液温度相行为。本研究提供了甲壳素多态自组装过程的丰富的原子水平视图，为甲壳素衍生的新型材料的合理设计铺平了道路。反平行链和平行链由不同的链间氢键介导。分析还表明，逆温度依赖性可能归因于疏水效应，让人想起低临界溶液温度相行为。本研究提供了甲壳素多态自组装过程的丰富的原子水平视图，为甲壳素衍生的新型材料的合理设计铺平了道路。反平行链和平行链由不同的链间氢键介导。分析还表明，逆温度依赖性可能归因于疏水效应，让人想起低临界溶液温度相行为。本研究提供了甲壳素多态自组装过程的丰富的原子水平视图，为甲壳素衍生的新型材料的合理设计铺平了道路。

更新日期：2023-08-01

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