2390-54-7

Thioflavin T (ThT) 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 is found to exist as micelles at concentrations commonly used to monitor fibrils by fluorescence assay (~10-20 μM). Specific conductivity changes are measured at varying concentration of Thioflavin T and the critical micellar concentration is calculated to be 4.0±0.5 μM. Changes in the fluorescence excitation and emission of Thioflavin T are also dependent on the micelle formation. The Thioflavin T micelles of 3 nm diameter are directly visualized using atomic force microscopy, and bound Thioflavin T micelles are 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 are 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.The micelles of Thioflavin T bind amyloid fibrils leading to enhancement of fluorescence emission.