Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, 2460, Riyadh 11451, Saudi Arabia.
Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia.
Int J Biol Macromol. 2023 Mar 1;230:123370. doi: 10.1016/j.ijbiomac.2023.123370. Epub 2023 Jan 21.
Protein aggregation and amyloid fibrillation are connected with neurodegenerative disorders. Insulin, a small molecular weight protein related to type II diabetes, has been shown to self-assemble to form protein aggregates. In this work, we investigated the effects of cetyltrimethylammonium bromide (CTAB) of insulin on the in vitro aggregation process at pH 7.4 and 2.0. The aggregation tendency of insulin was measured using a variety of biophysical approaches, including turbidity measurements, light scattering, far UV-CD, ThT dye binding, and transmission electron microscopy. The turbidity results demonstrated that at pH 7.4, a low concentration of CTAB (30-180 μM) causes insulin aggregation but at higer concentration (>180 μM) aggregation was not seen. However, at pH 2.0, both low as well as high concentrations of CTAB were unable to promote insulin aggregation. The ThT dye binding and far-UV CD data suggest that aggregation induced by CTAB is not having an ordered structure. Insulin treated with higher concentrations (>180 μM) of CTAB, the insulin gained a secondary structure. The possible cause of inducing aggregation in insulin is electrostatic and hydrophobic interaction because insulin contains a net negative charge at pH 7.4 and no aggregation at pH 2.0 due to electrostatic repulsion.
蛋白质聚集和淀粉样纤维形成与神经退行性疾病有关。胰岛素是一种与 2 型糖尿病相关的小分子蛋白，已被证明可以自行组装形成蛋白质聚集物。在这项工作中，我们研究了十六烷基三甲基溴化铵（CTAB）对 pH 7.4 和 2.0 时胰岛素体外聚集过程的影响。使用多种生物物理方法测量了胰岛素的聚集趋势，包括浊度测量、光散射、远紫外 CD、ThT 染料结合和透射电子显微镜。浊度结果表明，在 pH 7.4 时，低浓度（30-180 μM）的 CTAB 导致胰岛素聚集，但在高浓度（>180 μM）时则没有观察到聚集。然而，在 pH 2.0 时，低浓度和高浓度的 CTAB 都不能促进胰岛素聚集。ThT 染料结合和远紫外 CD 数据表明，CTAB 诱导的聚集没有形成有序结构。用高浓度（>180 μM）CTAB 处理的胰岛素获得了二级结构。在 pH 7.4 时，胰岛素中存在净负电荷，由于静电排斥，没有聚集，而在 pH 2.0 时没有聚集，这可能是由于静电和疏水相互作用诱导了胰岛素的聚集。
