淀粉样多肽在固体表面纳米水层中自组装行为研究

An aggregation of soluble amyloid peptides into the highly ordered fibrils has received considerable attentions because of the relevance to more than 20 neurodegenerative diseases. In fact, within a living cell amyloid peptides are in very crowded environments owing to an existence of many volume-excluding macromolecules such as proteins, polysaccharides and lipids. Previous studies have demonstrated that the behaviors of macromolecule in a confined space significantly differ from that in a diluted solution. In this project, a water nanofilm with controllable thickness on different solid surface is going to be prepared to mimic the confined space in a living cell. And the self-assembly of Islet Amyloid Polypeptide (IAPP) within the water nanofilm will be extensively studied. We try to explore the kinetics of amyloid fibril formation including the time evolution of morphologies and structures of IAPP aggregates with Bio-Atomic Force Microscopy. Particularly, the Tip Enhanced Raman Spectroscopy (TERS) will be utilized for characterizing the secondary structure and amino acid residue composition of the surface of an individual fibril, which is extremely valuable to infer which kinds of amino acids play a key role in fibril formation. In addition, the environmental effects such as the thickness of water nanofilm and the different solid surface on the self-assemble of IAPP within a water nanofilm will be also examined, which could provide an idea to further control the self-assembly of amyloid peptde within a confined space.

淀粉样多肽自组装与20多种神经退行性疾病密切相关，因此多肽自组装的动力学过程及其分子机理成了目前研究的热点。事实上细胞内部有很多大分子，多肽处于活动空间受限的生理环境中，研究表明受限于纳米尺度空间的生物分子其动力学行为和溶液相比有很大的差异。本项目拟利用固体表面形成的纳米水层来模拟与二型糖尿病相关的胰岛淀粉样多肽(IAPP)所处细胞内的拥挤环境。我们将通过原子力显微镜(AFM)详细研究IAPP在纳米水层中的自组装行为，包括组装体的表面形貌和力学性质随时间的演化规律。同时利用针尖增强拉曼光谱(TERS)测量IAPP组装体的精细结构，譬如单根纤维中β片层结构的氨基酸组成及其含量，并推测IAPP在空间受限条件下自组装过程起关键作用的氨基酸种类。另外，我们还将研究外界因素(如水层厚度和固体表面的物化性质)对IAPP在纳米水层中自组装的影响，为调控多肽在受限空间的自组装提供新的思路。

淀粉样多肽自组装与多种神经退行性疾病密切相关，人们期望通过研究影响多肽聚集的各种因素（如遗传、环境等）来探索相关疾病的发病机制。本项目我们研究了淀粉样纤维在二维水层的聚集过程和聚集机理，并和溶液中形成的纤维的结构形貌和力学性质进行对比。我们发现紧靠云母一层，多肽沿着云母晶格方向生长，形成较短但有序的纤维，其弹性模量大约是液体环境中纤维的2倍。同时我们发现金属铜离子能够明显抑制hIAPP多肽的聚集，而且能够诱导氧自由基的产生；而锌离子则能能够促进hIAPP的聚聚，通过氨基酸突变实验表明hIAPP中的H18不仅和多肽聚集密切相关而且对氧自由基的产生起到决定性的作用。另外，我们还以蛋白纤维为模板合成了尺寸可控、大小均匀的金属钯纳米颗粒，实验发现该纳米颗粒具有很好的催化特性，在化学催化上具有较大的应用前景。