The amyloid-β peptide is correlated with Alzheimer’s disease and is assumed to cause toxicity by its interaction with the neuron membrane. A custom-made microscope objective based on the supercritical angle technique was developed by our group, which allows investigation of interfacial events by performing surface-sensitive and low-invasive spectroscopy. Applied to Raman spectroscopy, this technique was used to collect information about the structure of polypeptides that interact with a supported lipid bilayer. Notably, the conformation used by amyloid-β(1–40) and amyloid-β(1–42) when interacting directly with or next to the supported lipid bilayer was characterized. We observed two distinct secondary structures, α-helix and β-sheet, which were exhibited by the peptide. These two structures were detected simultaneously. The propensity of the peptide to fold into these structures seemed dependent on both their number of amino acids and their proximity with the supported lipid bilayer. The α-helix structure was observed for amyloid-β(1–42) fragments that were closer to the lipid bilayer. Peptides that were located further away from the bilayer favored the β-sheet structure. Amyloid-β(1–40) was less prone to adopt the α-helix secondary structure.

中文翻译：

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超临界角拉曼显微镜在脂质双层的淀粉样蛋白聚集体的结构分析。

淀粉样蛋白-β肽与阿尔茨海默氏病相关，并被认为通过与神经元膜的相互作用而引起毒性。我们小组开发了一种基于超临界角技术的定制显微镜物镜，它可以通过执行表面敏感和低侵入性光谱学来研究界面事件。应用于拉曼光谱学时，该技术用于收集有关与支持的脂质双层相互作用的多肽结构的信息。值得注意的是，当与受支持的脂质双层直接或相邻相互作用时，淀粉样蛋白-β（1-4）和淀粉样蛋白-β（1-42）所使用的构象已得到表征。我们观察到该肽表现出两个不同的二级结构，α-螺旋和β-折叠。同时检测到这两个结构。肽折叠成这些结构的倾向似乎取决于它们的氨基酸数目和与支持的脂质双层的接近性。观察到更靠近脂质双层的淀粉样蛋白β（1-42）片段的α-螺旋结构。距离双层更远的肽倾向于β-折叠结构。淀粉样蛋白-β（1–40）不易采用α-螺旋二级结构。