Alzheimer's disease is a severe brain condition caused by the formation of amyloid plaques composed of amyloid beta (Aβ) peptides. These peptides form oligomers, protofibrils, and fibrils before deposition into amyloid plaques. Among these intermediates, Aβ oligomers (AβOs) were found to be the most toxic and therefore an appealing target for drug development and understanding their role in the disease. However, precise isolation and characterization of AβOs have proven challenging because AβOs tend to aggregate and form heterogeneous mixtures in solution. As a solution, we genetically fused the Aβ peptide with a ferritin monomer. Such fusion allowed the encapsulation of precisely 24 Aβ peptides inside the 24-mer ferritin cage. Using high-speed atomic force microscopy (HS-AFM), we disassembled ferritin and directly visualized the Aβ core enclosed within the cage. The thioflavin-T assay (ThT) and attenuated total reflection infrared spectroscopy (ATR-IR) revealed the presence of a β-sheet structure in the encapsulated oligomeric aggregate. Gallic acid, an amyloid inhibitor, can inhibit the fluorescence of ThT bound AβOs. Our approach represents a significant advancement in the isolation and characterization of β-sheet rich AβOs and is expected to be useful for future studies of other disordered peptides such as α-synuclein and tau.

中文翻译：

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β 淀粉样蛋白与铁蛋白融合，在铁蛋白笼内产生分离的富含 β 折叠寡聚体的聚集体

阿尔茨海默病是一种严重的脑部疾病，由β-淀粉样蛋白 (Aβ) 肽组成的淀粉样斑块的形成引起。这些肽在沉积成淀粉样斑块之前形成寡聚体、原纤维和原纤维。在这些中间体中，Aβ 寡聚物 (AβO) 被发现毒性最强，因此成为药物开发和了解其在疾病中的作用的有吸引力的目标。然而，AβO 的精确分离和表征已被证明具有挑战性，因为 AβO 在溶液中倾向于聚集并形成异质混合物。作为解决方案，我们将 Aβ 肽与铁蛋白单体进行基因融合。这种融合使得 24 个 Aβ 肽精确地封装在 24 聚体铁蛋白笼内。使用高速原子力显微镜 (HS-AFM)，我们拆解了铁蛋白并直接观察到笼内封闭的 Aβ 核心。硫黄素-T 测定 (ThT) 和衰减全反射红外光谱 (ATR-IR) 揭示了封装的低聚物聚集体中存在 β-折叠结构。没食子酸是一种淀粉样蛋白抑制剂，可以抑制 ThT 结合的 AβO 的荧光。我们的方法代表了富含 β-折叠的 AβO 的分离和表征方面的重大进步，预计可用于其他无序肽（例如 α-突触核蛋白和 tau）的未来研究。