Some recent studies have shown that the surface and interface play an important role in the assembly and aggregation of amyloid proteins. However, it is unclear how the gas–liquid interface affects the protein assembly at the nanometer scale although the presence of gas–liquid interfaces is very common in in vitro experiments. Nanobubbles have a large specific surface area, which provides a stage for interactions with various proteins and peptides on the nanometer scale. In this work, nanobubbles produced in solution were employed for studying the effects of the gas–liquid interface on the assembly of glucagon proteins. Atomic force microscopy (AFM) studies showed that nanobubble-treated glucagon solution formed fibrils with an apparent height of 4.02 ± 0.71 nm, in contrast to the fibrils formed with a height of 2.14 ± 0.53 nm in the control. Transmission electron microscopy (TEM) results also showed that nanobubbles promoted the assembly of glucagon to form more fibrils. Thioflavin T (ThT) fluorescence and Fourier transform infrared (FTIR) analyses indicated that the nanobubbles induced the change of the glucagon conformation to a β-sheet structure. A mechanism that explains how nanobubbles affect the assembly of glucagon amyloid fibrils was proposed based on the above-mentioned experimental results. Given the fact that there are a considerable amount of nanobubbles existing in protein solutions, our results indicate that nanobubbles should be considered for fully understanding the protein aggregation events in vitro.

中文翻译：

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纳米气泡对胰高血糖素淀粉样蛋白原纤维组装的影响

最近的一些研究表明，表面和界面在淀粉样蛋白的组装和聚集中起着重要作用。然而，尽管在体外气液界面的存在非常普遍，但目前尚不清楚气液界面如何影响纳米级的蛋白质组装。实验。纳米气泡具有大的比表面积，这提供了与纳米级的各种蛋白质和肽相互作用的阶段。在这项工作中，溶液中产生的纳米气泡被用于研究气液界面对胰高血糖素蛋白组装的影响。原子力显微镜（AFM）研究表明，纳米气泡处理的胰高血糖素溶液形成原纤维，其表观高度为4.02±0.71 nm，而对照组中原纤维的高度为2.14±0.53 nm。透射电子显微镜（TEM）的结果还表明，纳米气泡促进了胰高血糖素的组装，从而形成了更多的原纤维。硫黄素T（ThT）荧光和傅立叶变换红外（FTIR）分析表明，纳米气泡可诱导胰高血糖素构象改变为β-折叠结构。基于上述实验结果，提出了解释纳米气泡如何影响胰高血糖素淀粉样蛋白原纤维组装的机制。考虑到蛋白质溶液中存在大量纳米气泡的事实，我们的结果表明应考虑使用纳米气泡以充分了解蛋白质聚集事件体外。