聚肽超螺旋的组装机理及多层次手性研究

The helical structure is one of the most fundamental geometrical shapes in nature, which can be found at all length scales. Chirality is the basic characteristic of helices, which is closely related to the property of the helical structures. Thus controlling the chirality of helical structure is a fundamental scientific task. Polypeptide block copolymer/homopolymer mixtures are capable of self-assembling into supramolecular helical structures (super-helices), in which homopolymers aggregate into bundles and serve as core of the super-helices, while polypeptide block copolymers helically warp into screws of the super-helices. The chirality of the super-helices is uniform in either right-handed or left-handed form, which can be adjusted by solvent and solution temperature. .In this proposal, we plan to synthesize a series of polypeptide homopolymers and polypeptide copolymers with various topologies. By assembling and then crosslinking of the polypeptide copolymer consisting of crosslinkable segments, polypeptide nano-rods can be prepared. We then perform the self-assembly research of polypeptide copolymer/homopolymer mixtures and polypeptide copolymer/nano-rod mixtures to unveil the law for the formation of the super-helices. Subsequently, we intend to further investigate the influence of handedness of the polypeptide α-helix and experimental conditions such as solvent and solution temperature on the chirality of the super-helices. In the same time, the chirality of the helical stacking of the pending benzyl group in polypeptide chains is also characterized. Then the chirality relationship among super-helix, polypeptide α-helix and the helical stacking of pending benzyl groups is specified, and the mechanism behind that controls the chirality of the super-helices is further revealed. The results gained could be useful for understanding the structure of super-helix and other complex structures, and providing valuable information and guidance for controllable preparation of super-helix, as well as the further applications.

手性是螺旋结构的最基本特征，与其性能有密切关系，手性控制是基本科学问题。聚肽共聚物/均聚物共混体系可以自组装形成超螺旋：均聚物聚集成束构成内核，共聚物以均聚物束为模板形成螺纹，其手性可以通过温度和溶剂来调控。.本项目拟合成一系列聚肽均聚物和不同拓扑结构的聚肽共聚物，并以含有交联基团的聚肽共聚物制备聚肽纳米棒。研究共聚物/均聚物或共聚物/纳米棒共混体系的自组装行为，掌握共聚物和均聚物/纳米棒的结构对超螺旋结构的影响。在此基础上，研究聚肽α-螺旋分子链的手性和环境条件（温度和溶剂等）对超螺旋手性的影响；并表征聚肽苯环侧基堆叠的手性与环境条件的关系。通过研究，明确超螺旋、聚肽分子链α-螺旋和聚肽苯环侧基堆叠三个层次手性之间的关系，揭示超螺旋手性的控制规律，掌握超螺旋的组装机理。研究工作有助于加深对超螺旋等复杂结构的理解，为超螺旋结构的可控制备提供指导，为其应用打下基础。

本项目中，对聚肽共聚物/均聚物共组装所形成的超分子螺旋的结构、形貌控制以及手性转变机理作了系统深入的研究。研究了起始溶剂性质、实验温度和聚肽分子的手性对超分子螺旋手性的影响规律，通过对超螺旋的手性、聚肽分子链手性、以及苯环侧基堆叠方向手性三个不同层次手性之间关系的分析，明确三个层次手性信息之间的关系，揭示超螺旋手性的控制因素和转变规律。还发现共聚物和均聚物共混比例、嵌段共聚物分子量等因素也影响超分子螺旋的手性。基于以上发现，提出了侧基苯环排列手性决定超分子螺旋手性的创新学术思想。另外，通过聚肽均聚物的分子量调控了超分子螺旋的形貌，随着聚肽均聚物分子量的增加，超分子螺旋的形貌由均匀的棒状转变为均匀的环状。.研究了聚肽共聚物自组装胶束的超分子反应，通过控制溶剂组分和溶液温度，实现了胶束的聚合反应（符合逐步聚合原理）和成环反应（单个胶束弯曲并首尾相接而成）。还将研究拓展到微尺度模板表面的自组装（界面自组装），发现聚肽共聚物在微粒子模板表面自组装形成了点状表面胶束，这些胶束的排列符合欧拉定律，即五元排列与七元排列胶束的个数之差为12；发现聚肽共聚物在微条带表面自组装手性条带图案，手性参数可以通过微条带模板的宽度来调控。.通过研究，深化了对聚肽超分子螺旋手性转变现象的认识，提出了侧基苯环排列手性决定超分子螺旋手性的创新学术思想；将聚肽自组装研究从溶液分子层次拓展到微模板表面和超分子领域，开创了新的研究方向。