Solvent Controlled Structural Transition of KI4K Self-Assemblies: from Nanotubes to Nanofibrils
Solvent Controlled Structural Transition of KI4K Self-Assemblies: from Nanotubes to Nanofibrils
复制标题
溶剂控制的 KI4K 自组装结构转变：从纳米管到纳米原纤维
作者：
Zhao Rurong;Deng Li;Wang Jiqian;Xu Hai;Lu Jian R
在良好控制的条件下对肽和蛋白质组装体进行结构调控具有重要的基础和实际意义。尽管进行了广泛的研究，但以可控的方式调节自组装纳米结构仍然具有巨大的挑战性，因为自组装过程由各种非共价相互作用及其相互作用决定。我们在这里报告如何操纵设计的，对称的两亲性肽（KI 4K）通过溶剂控制的结构转变的自组装。结构转变过程仔细遵循的组合，透射电子显微镜（TEM），原子力显微镜（AFM），圆二色性（CD），傅里叶变换红外光谱（FTIR），和小角中子散射（SANS）。结果表明，乙腈的引入显著影响了疏水侧链间的疏水相互作用，而对肽骨架间的β-折叠氢键影响不大.随着乙腈的加入，由于疏水相互作用的减弱以及随之而来的KI 4K β-片层之间横向堆叠的减弱，发生了从纳米管到螺旋/扭曲带，然后到细原纤维的结构转变。由于分子的对称性，赖氨酸侧链氨基间的静电斥力增加对KI 4K β-折叠的横向堆积影响不大。互补分子动力学（MD）模拟也表明，溶剂化的乙腈分子到疏水域削弱相邻的片之间的连贯性。
The structural modulation of peptide and protein assemblies under well-controlled conditions is of both fundamental and practical significance. In spite of extensive studies, it remains hugely challenging to tune the self-assembled nanostructures in a controllable manner because the self-assembly processes are dictated by various noncovalent interactions and their interplay. We report here how to manipulate the self-assembly of a designed, symmetric amphiphilic peptide (KI4K) via the solvent-controlled structural transition. Structural transition processes were carefully followed by the combination of transmission electronic microscopy (TEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), and small angle neutron scattering (SANS). The results show that the introduction of acetonitrile into water significantly affected the hydrophobic interactions among hydrophobic side chains while imposing little impact on the β-sheet hydrogen bonding between peptide backbones. A structural transition occurred from nanotubes to helical/twisted ribbons and then to thin fibrils with the addition of acetonitrile due to the reduced hydrophobic interactions and the consequent weakening of the lateral stacking between KI4K β-sheets. The increased intermolecular electrostatic repulsions among lysine side chain amino groups had little effect on the lateral stacking of KI4K β-sheets due to the molecular symmetry. Complementary molecular dynamic (MD) simulations also indicated the solvation of acetonitrile molecules into the hydrophobic domains weakening the coherence between the neighboring sheets.