Thioflavin T is a benzothiazole dye that exhibits enhanced fluorescence upon binding to amyloid fibrils and is commonly used to diagnose amyloid fibrils, both ex vivo and in vitro. In aqueous solutions, thioflavin T was found to exist as micelles at concentrations commonly used to monitor fibrils by fluorescence assay (∼10-20 μM). Specific conductivity changes were measured at varying concentration of thioflavin T and the critical micellar concentration was calculated to be 4.0 ± 0.5 μM. Interestingly, changes in the fluorescence excitation and emission of thioflavin T were also dependent on the micelle formation. The thioflavin T micelles of 3 nm diameter were directly visualized using atomic force microscopy, and bound thioflavin T micelles were observed along the fibril length for representative fibrils. Increasing concentration of thioflavin T above the critical micellar concentration shows increased numbers of micelles bound along the length of the amyloid fibrils. Thioflavin T micelles were disrupted at low pH as observed by atomic force microscopy and fluorescence enhancement upon binding of thioflavin T to amyloid fibrils also reduced by several-fold upon decreasing the pH to below 3. This suggests that positive charge on the thioflavin T molecule has a role in its micelle formation that then bind the amyloid fibrils. Our data suggests that the micelles of thioflavin T bind amyloid fibrils leading to enhancement of fluorescence emission. © 2005 Elsevier Inc. All rights reserved.
CITATION STYLE
Khurana, R., Coleman, C., Ionescu-Zanetti, C., Carter, S. A., Krishna, V., Grover, R. K., … Singh, S. (2005). Mechanism of thioflavin T binding to amyloid fibrils. Journal of Structural Biology, 151(3), 229–238. https://doi.org/10.1016/j.jsb.2005.06.006
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