Structural Studies of Alzheimer's beta-Amyloid Fibrils

于二零一五财政年度，本集团在以下方面取得进展： (1)来自脑组织的淀粉样纤维结构：与伦敦大学学院的John Collinge教授合作，我们获得了来自四类AD患者尸检的36个脑组织样本的纤维的固态NMR和电子显微镜数据（典型的长期病史、后皮质萎缩、短期病程、非痴呆）。 使用我们公开的淀粉样蛋白提取和接种方案，使用40-残基和42-残基β-淀粉样蛋白肽制备同位素标记的原纤维。 固态NMR数据表明，大多数AD患者在他们的大脑中形成相同的主要的40个残基的原纤维结构，但持续时间短的患者可以形成不同的和更异质的结构。 42残基原纤维的结果表明，患者类别和分子结构之间没有明确的相关性。 我们已经探索了各种数据分析方法，现在正在撰写报告这些结果的手稿。 (2)β-淀粉样蛋白组装过程的固态核磁共振研究：我们已经使用固态核磁共振来检查β-淀粉样蛋白肽从单体状态到寡聚状态到原纤维状态，最后到真正的淀粉样蛋白纤维状态的构象变化和超分子组织变化的进展。 这些实验是由我们实验室研制的低温动态核极化装置实现的。 我们发现，主要的构象特征（两个单独的β-链段）是存在的，即使在最早阶段的自组装，但构象顺序的程度单调增加。 此外，对齐的平行β-折叠结构直到最终的淀粉样原纤维状态才出现。 这项工作已发表在J。Chem. Soc.

Progress in FY2015 has been in the following areas: (1) AMYLOID FIBRIL STRUCTURES DERIVED FROM BRAIN TISSUE: In collaboration with Prof. John Collinge of University College London, we have obtained solid state NMR and electron microscopy data for fibrils derived from 36 brain tissue samples from autopsies of AD patients in four categories (typical long history, posterior cortical atrophy, short duration, nondemented). Using our published amyloid extraction and seeding protocols, isotopically labeled fibrils were prepared using both 40-residue and 42-residue beta-amyloid peptides. The solid state NMR data suggest that most AD patients develop the same predominant 40-residue fibril structure in their brains, but that short duration patients can develop different and more heterogeneous structures. Results for 42-residue fibrils indicate no clear correlation between patient category and molecular structure. We have explored various approaches to data analysis, and are now in the process of writing a manuscript to report these results. (2) SOLID STATE NMR STUDIES OF THE BETA-AMYLOID ASSEMBLY PROCESS: We have used solid state NMR to examine the progression of conformational changes and changes in supramolecular organization as the beta-amyloid peptide goes from a monomeric state to an oligomeric state to a protofibrillar state and finally to a true amyloid fibril state. These experiments are enabled by the low-temperature dynamic nuclear polarization apparatus developed in our lab. We find that the principal conformational features (two separate beta-strand segments) are present even at the earliest stages of self-assembly, but that the degree of conformational order increases monotonically. Moreover, the in-register parallel beta-sheet structure does not appear until the final amyloid fibril state. This work has been published in J. Am. Chem. Soc.