Structure et Fonction des Membranes Biologiques, Université libre de Bruxelles, B-1050 Bruxelles, Belgique.
Laboratoire de Chimie Physique d'Orsay, CNRS UMR8000, Université Paris-Sud, Université Paris-Saclay, F-91400 Orsay, France.
Molecules. 2020 Jun 24;25(12):2899. doi: 10.3390/molecules25122899.
Amyloid fibrils are composed of aggregated peptides or proteins in a fibrillar structure with a higher β-sheet content than in their native structure. To characterize them, we used an innovative tool that coupled infrared spectroscopy with atomic force microscopy (AFM-IR). With this method, we show that we can detect different individual aggregated species from oligomers to fibrils and study their morphologies by AFM and their secondary structures based on their IR spectra. AFM-IR overcomes the weak spatial resolution of usual infrared spectroscopy and achieves a resolution of ten nanometers, the size of isolated fibrils. We characterized oligomers, amyloid fibrils of Aβ42 and fibrils of α-synuclein. To our surprise, we figured out that the nature of some surfaces (ZnSe) used to study the samples induces destructuring of amyloid samples, leading to amorphous aggregates. We strongly suggest taking this into consideration in future experiments with amyloid fibrils. More importantly, we demonstrate the advantages of AFM-IR, with a high spatial resolution (≤ 10 nm) allowing spectrum recording on individual aggregated supramolecular entities selected thanks to the AFM images or on thin layers of proteins.
淀粉样纤维由聚集的肽或蛋白质组成，具有纤维状结构，其β-折叠含量高于其天然结构。为了表征它们，我们使用了一种创新的工具，将红外光谱与原子力显微镜（AFM-IR）结合使用。通过这种方法，我们表明我们可以检测到不同的聚集物种，从低聚物到纤维，并通过 AFM 研究它们的形态，根据它们的红外光谱研究它们的二级结构。AFM-IR 克服了常规红外光谱空间分辨率弱的问题，实现了 10 纳米的分辨率，即孤立纤维的大小。我们对寡聚物、Aβ42 淀粉样纤维和α-突触核蛋白纤维进行了表征。令我们惊讶的是，我们发现一些用于研究样品的表面（ZnSe）的性质会导致淀粉样样品的去结构化，导致无定形聚集。我们强烈建议在未来的淀粉样纤维实验中考虑到这一点。更重要的是，我们展示了 AFM-IR 的优势，具有高空间分辨率（≤10nm），允许在 AFM 图像选择的单个聚集超分子实体上或在蛋白质的薄层上记录光谱。
