School of Chemistry, National University of Ireland Galway, Galway H91 TK33, Ireland.
Biointerphases. 2020 Dec 17;15(6):061011. doi: 10.1116/6.0000620.
It has long been recognized that liquid interfaces, such as the air-water interface (AWI), can enhance the formation of protein fibrils. This makes liquid interfaces attractive templates for fibril formation but fully realizing this requires knowledge of protein behavior at interfaces, which is currently lacking. To address this, molecular dynamics simulation is used to investigate fragments of amyloid beta, a model fibril forming protein, at the air-water interface. At the air-water interface, the enrichment of aggregation-prone helical conformations provides a mechanism for the enhancement of fibrillation at interfaces. The conformational ensemble at the air-water interface was also considerably reduced compared to bulk solution due to the tendency of hydrophobic side chains partitioning into the air restricting the range of conformations. Little overlap between the conformational ensembles at the AWI and in the bulk solution was found, suggesting that AWI induces the formation of a different set of structures compared to bulk solution. The smaller Aβ(16-22) and Aβ(25-35) fragments show an increase in the propensity for an ordered secondary structure at the air-water interface but with a increased propensity for turn over other motifs, illustrating the importance of intra-protein interactions for stabilizing helical and extended conformations.
长期以来，人们已经认识到液体界面（如气-水界面，air-water interface，简称 AWI）可以促进蛋白质纤维的形成。这使得液体界面成为纤维形成的有吸引力的模板，但要充分实现这一点，需要了解蛋白质在界面上的行为，而目前这方面的知识还很缺乏。为了解决这个问题，我们使用分子动力学模拟研究了淀粉样β（amyloid beta）的片段，这是一种模型纤维形成蛋白，位于气-水界面。在气-水界面上，富含聚集倾向的螺旋构象，为界面上的纤维增强提供了一种机制。与本体溶液相比，由于疏水性侧链倾向于分配到空气中，从而限制了构象的范围，因此气-水界面上的构象集合也大大减少。在 AWI 和本体溶液中的构象集合之间发现很少有重叠，这表明与本体溶液相比，AWI 诱导了形成一组不同的结构。较小的 Aβ（16-22）和 Aβ（25-35）片段在气-水界面上表现出增加有序二级结构的倾向，但其他模体的构象翻转倾向增加，这说明了蛋白质内相互作用对于稳定螺旋和扩展构象的重要性。
