Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur-721302, India.
Phys Chem Chem Phys. 2019 Sep 18;21(36):20083-20094. doi: 10.1039/c9cp03238j.
The formation of amyloid aggregates is the hallmark of many protein misfolding diseases, including Type-II diabetes mellitus, which is caused by the fibrillation of amylin protein. It is established that nano-sized ligands such as curcumin, resveratrol and graphene quantum dots can modify protein aggregation rates. In this article, we report a comparative study of these ligands to estimate their protein aggregation rates and fluorescence quenching using various experimental techniques. Through light scattering experiments, the RH of bare amylin was found to increase at a rate of 43% per day, whereas in the presence of the ligands in different molar ratios (A1C10, A1R10 and A1GQDs20), the sizes of the complexes were found to grow at rates of 7%, 8% and 13% per day, respectively. We observed fluorescence quenching using photoluminescence experiments for all three protein-ligand complexes. The protein aggregation rate and fluorescence quenching exhibited a concentration-dependent competitive role in the inhibition process. Interestingly, for graphene quantum dots, the protein aggregation rate is more affected at lower concentrations, while fluorescence quenching dominates at higher concentrations; this is in contrast to curcumin and resveratrol, where fluorescence quenching dominates at all concentrations of the ligands in the complex. The FTIR data showed appreciable conversion of β-sheets into less aggregation-prone secondary structures for all three amylin-ligand ratios; however, the inhibition performance of curcumin overshadowed those of the other two inhibitors. The inhibition behavior of these three ligands was corroborated by analysis of analytical and high-resolution TEM images of the fibrils.
淀粉样纤维的形成是许多蛋白质错误折叠疾病的标志，包括由胰岛淀粉样多肽（Amylin）蛋白纤维形成导致的 2 型糖尿病。研究表明，纳米级配体如姜黄素、白藜芦醇和石墨烯量子点可以改变蛋白质的聚集速率。在本文中，我们报告了对这些配体的比较研究，以使用各种实验技术估计它们的蛋白质聚集速率和荧光猝灭。通过光散射实验，发现裸淀粉样蛋白的 RH 每天增加 43%，而在不同摩尔比（A1C10、A1R10 和 A1GQDs20）的配体存在下，复合物的大小每天分别以 7%、8%和 13%的速率增长。我们通过光致发光实验观察到所有三种蛋白质-配体复合物的荧光猝灭。在抑制过程中，蛋白质聚集速率和荧光猝灭表现出浓度依赖性的竞争作用。有趣的是，对于石墨烯量子点，在较低浓度下，蛋白质聚集速率受影响更大，而在较高浓度下，荧光猝灭占主导地位；这与姜黄素和白藜芦醇不同，在复合物中配体的所有浓度下，荧光猝灭都占主导地位。FTIR 数据显示，对于所有三种淀粉样蛋白-配体比例，β-片层都有相当大的转化为不易聚集的二级结构；然而，姜黄素的抑制性能超过了其他两种抑制剂。通过对纤维的分析和高分辨率 TEM 图像的分析，证实了这三种配体的抑制行为。
