In neurodegenerative diseases, a wide range of amyloid proteins or peptides such as amyloid-beta and α-synuclein fail to keep native functional conformations, followed by misfolding and self-assembling into a diverse array of aggregates. The aggregates further exert toxicity leading to the dysfunction, degeneration and loss of cells in the affected organs. Due to the disordered structure of the amyloid proteins, endogenous molecules, such as lipids, are prone to interact with amyloid proteins at a low concentration and influence amyloid cytotoxicity. The heterogeneity of amyloid proteinscomplicates the understanding of the amyloid cytotoxicity when relying only on conventional bulk and ensemble techniques. As complementary tools, single-molecule techniques (SMTs) provide novel insights into the different subpopulations of a heterogeneous amyloid mixture as well as the cytotoxicity, in particular as involved in lipid membranes. This review focuses on the recent advances of a series of SMTs, including single-molecule fluorescence imaging, single-molecule force spectroscopy and single-nanopore electrical recording, for the understanding of the amyloid molecular mechanism. The working principles, benefits and limitations of each technique are discussed and compared in amyloid protein related studies.. We also discuss why SMTs show great potential and are worthy of further investigation with feasibility studies as diagnostic tools of neurodegenerative diseases and which limitations are to be addressed.

中文翻译：

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淀粉样蛋白的单分子研究：从生物物理特性到诊断观点

在神经退行性疾病中，广泛的淀粉样蛋白或肽，例如淀粉样蛋白-β 和α-突触核蛋白未能保持天然功能构象，随后错误折叠和自组装成各种聚集体。聚集体进一步发挥毒性，导致受影响器官中的细胞功能障碍、退化和损失。由于淀粉样蛋白的无序结构，内源性分子，如脂质，容易与低浓度的淀粉样蛋白相互作用，影响淀粉样蛋白的细胞毒性。淀粉样蛋白的异质性使仅依赖传统的散装和集成技术时对淀粉样蛋白细胞毒性的理解变得复杂。作为补充工具，单分子技术 (SMT) 提供了对异质淀粉样蛋白混合物的不同亚群以及细胞毒性的新见解，特别是涉及脂质膜的细胞毒性。本综述重点介绍了一系列 SMT 的最新进展，包括单分子荧光成像、单分子力谱和单纳米孔电记录，以了解淀粉样蛋白的分子机制。在淀粉样蛋白相关研究中讨论和比较了每种技术的工作原理、益处和局限性。我们还讨论了为什么 SMT 显示出巨大的潜力并值得进一步调查，可行性研究作为神经退行性疾病的诊断工具，以及哪些局限性是解决。