Institut de Physique de Rennes, UMR 6251 CNRS & Universite Rennes 1, 263 Avenue du general Leclerc, F-35042 Rennes Cedex, France.
J Am Chem Soc. 2010 Mar 31;132(12):4230-41. doi: 10.1021/ja9088023.
Nanofabrication by molecular self-assembly involves the design of molecules and self-assembly strategies so that shape and chemical complementarities drive the units to organize spontaneously into the desired structures. The power of self-assembly makes it the ubiquitous strategy of living organized matter and provides a powerful tool to chemists. However, a challenging issue in the self-assembly of complex supramolecular structures is to understand how kinetically efficient pathways emerge from the multitude of possible transition states and routes. Unfortunately, very few systems provide an intelligible structure and formation mechanism on which new models can be developed. Here, we elucidate the molecular and supramolecular self-assembly mechanism of synthetic octapeptide into nanotubes in equilibrium conditions. Their complex hierarchical self-assembly has recently been described at the mesoscopic level, and we show now that this system uniquely exhibits three assembly stages and three intermediates: (i) a peptide dimer is evidenced by both analytical centrifugation and NMR translational diffusion experiments; (ii) an open ribbon and (iii) an unstable helical ribbon are both visualized by transmission electron microscopy and characterized by small angle X-ray scattering. Interestingly, the structural features of two stable intermediates are related to the final nanotube organization as they set, respectively, the nanotube wall thickness and the final wall curvature radius. We propose that a specific self-assembly pathway is selected by the existence of such preorganized and stable intermediates so that a unique final molecular organization is kinetically favored. Our findings suggests that the rational design of oligopeptides can encode both molecular- and macro-scale morphological characteristics of their higher-order assemblies, thus opening the way to ultrahigh resolution peptide scaffold engineering.
分子自组装的纳米制造涉及分子和自组装策略的设计，以便形状和化学互补性驱动单元自发组织成所需的结构。自组装的强大功能使其成为有生命的组织物质无处不在的策略，并为化学家提供了强大的工具。然而，在复杂超分子结构的自组装中，一个具有挑战性的问题是理解如何从众多可能的过渡态和途径中出现动力学有效的途径。不幸的是，很少有系统提供可以开发新模型的可理解结构和形成机制。在这里，我们阐明了在平衡条件下合成八肽自组装成纳米管的分子和超分子自组装机制。它们复杂的层次自组装最近在介观水平上被描述，我们现在表明，这个系统独特地表现出三个组装阶段和三个中间体：（i）通过分析离心和 NMR 平移扩散实验都证明了肽二聚体的存在；（ii）开放的带状物和（iii）不稳定的螺旋带状物都通过透射电子显微镜可视化，并通过小角 X 射线散射进行了表征。有趣的是，两个稳定中间体的结构特征与最终纳米管的组织有关，因为它们分别设定了纳米管壁的厚度和最终壁曲率半径。我们提出，通过存在这种预组织和稳定的中间体，可以选择特定的自组装途径，从而有利于动力学上独特的最终分子组织。我们的发现表明，寡肽的合理设计可以编码其高级组装的分子和宏观尺度形态特征，从而为超高分辨率肽支架工程开辟了道路。
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