Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (6): 1391-1396.

• ARTICLE •

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

Song LI,Fu-Feng LIU,Lin-Ling YU,Yan-Jiao ZHAO,Xiao-Yan DONG*()

• Received:2016-01-04 Published:2016-06-03
• Contact: Xiao-Yan DONG E-mail:d_xy@tju.edu.cn
• Supported by:
National Natural Science Foundation of China(21236005, 21376172, 21406160, 21576199)

Abstract:

The fluorescent dye thioflavin T (ThT) is widely used for the qualitative and quantitative detection of amyloid fibrils. However, many small-molecular inhibitors have been shown to compete with ThT in binding the fibrils and therefore greatly affect the ThT fluorescence. The effect of ThT 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 ThT 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 ThT concentration at low ranges, but then begins to increase beyond a specific ThT concentration, which itself increases with Aβ40 concentration. By contrast, the elongation rate slowly increases with ThT concentration. As for the secondary structure and morphology of the fibrils, no significant effects of ThT are observed. Isothermal titration calorimetry suggests that the hydrophobic interaction dominates the binding of ThT to Aβ40. Based on these findings, a working mechanism of the dual effects of ThT on Aβ fibrillization is proposed. These results should aid our understanding of the molecular mechanism of ThT binding with Aβ and allow practical improvements in the measurement of the nucleation kinetics of Aβ fibrillization.

MSC2000:

• O641