In this work, nine kinds of amino acid residues, i.e., alanine (A), leucine (L), valine (V), isoleucine (I), tryptophan (W), glutamine (Q), threonine (T), serine (S), and cysteine (C), were selected to construct seven cyclic peptide nanotubes (CPNTs) with diverse hydrophilic/hydrophobic external surfaces, which were further separately inserted at the water/hexane interface to investigate their microstructures and interfacial properties. Molecular dynamics (MD) simulations reveal that all the CPNTs except the QT- and VL-CPNTs have different degrees of tilt, fracture, and shedding at the interface. The end-CPs are more susceptible to the effect of the surroundings than the mid-CPs. The interactions of individual CP subunits with the neighborings disclose the firmness of the mid-CPs and the dissociation of the end-CPs. The results indicate that a hydrophobic CPNT is prone to stay at the interface, while a hydrophilic CPNT easily enters the water phase, resulting in many H-bonds with water. Results in this work enrich the dynamic properties of a hydrophilic/hydrophobic CPNT at the biphase interface at the atomic level.

中文翻译：

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亲水/疏水环肽纳米管在水/己烷界面上行为的分子动力学模拟

在这项工作中，有9种氨基酸残基，即丙氨酸（A），亮氨酸（L），缬氨酸（V），异亮氨酸（I），色氨酸（W），谷氨酰胺（Q），苏氨酸（T），丝氨酸（选择S）和半胱氨酸（C）来构建七个具有各种亲水/疏水外表面的环状肽纳米管（CPNT），将其进一步分别插入水/己烷界面以研究其微观结构和界面特性。分子动力学（MD）模拟显示，除QT-和VL-CPNT以外，所有CPNT在界面处都有不同程度的倾斜，断裂和脱落。与中部CP相比，最终CP更容易受到周围环境的影响。各个CP亚基与邻近分子的相互作用揭示了中CP的牢固性和末端CP的解离。结果表明，疏水性CPNT容易留在界面上，而亲水性CPNT容易进入水相，导致许多与水的氢键结合。这项工作的结果丰富了亲水/疏水CPNT在原子级双相界面处的动态特性。