硫黄素T对淀粉样β-蛋白质40聚集成核动力学的双重影响(英文)

Dual Effect of Thioflavin T on the Nucleation Kinetics of Amyloid β-Protein 40

荧光染料硫黄素T常用于淀粉样纤维聚集过程的定性定量检测。虽然有研究表明,某些抑制淀粉样蛋白质聚集的小分子抑制剂会与硫黄素T相互作用,影响其测试结果。但硫黄素T如何影响淀粉样蛋白质的聚集成核动力学尚不清晰。本文以淀粉样β-蛋白质40(Aβ40)为模型,系统研究了硫黄素T对Aβ40聚集成核的影响。研究发现:硫黄素T能够显著改变Aβ40的聚集成核动力学,且影响程度与硫黄素T的浓度密切相关。即在低浓度硫黄素T存在下,Aβ40成核速率的延迟时间先随着硫黄素T浓度的升高而缩短,后随着硫黄素T浓度的升高延迟时间反而延长。但延伸的速率却随硫黄素T浓度的升高而缓慢增大。另外,硫黄素T基本不会影响Aβ40的二级结构和纤维形态。同时,等温滴定微量热实验结果表明,硫黄素T结合Aβ40之间的主要作用力为疏水相互作用。据此,本研究提出硫黄素T对Aβ40聚集成核动力学的双重影响机理。这些结果有助于进一步了解硫黄素T与淀粉样蛋白质的作用特点,为今后硫黄素T在Aβ40聚集成核动力学实验中的使用提供参考。

The fluorescent dye thioflavin T（Th T） is widely used for the qualitative and quantitative detection of amyloid fibrils.However,many small-molecular inhibitors have been shown to compete with Th T in binding the fibrils and therefore greatly affect the Th T fluorescence.The effect of Th T on the aggregation kinetics of amyloid proteins is not yet fully understood.Here,using amyloid β-protein 40（Aβ40） as a model system,we show that Th T significantly alters the aggregation kinetics of Aβ40 in a dose-dependent manner,leading to a decrease-increase trend in the lag time that represents the nucleation rate.Specifically,the lag time decreases as a function of Th T concentration at low ranges,but then begins to increase beyond a specific Th T concentration,which itself increases with Aβ40 concentration.By contrast,the elongation rate slowly increases with Th T concentration.As for the secondary structure and morphology of the fibrils,no significant effects of Th T are observed.Isothermal titration calorimetry suggests that the hydrophobic interaction dominates the binding of Th T to Aβ40.Based on these findings,a working mechanism of the dual effects of Th T on Aβfibrillization is proposed.These results should aid our understanding of the molecular mechanism of Th T binding with Aβ and allow practical improvements in the measurement of the nucleation kinetics of Aβ fibrillization.