Thioflavin T Fluorescent method: what color does amyloid fluoresce?

• A. Yellow to yellow green
• B. Red
• C. Blue
• D. Magenta

Answer: (A)

Thioflavin T fluoresces in the yellow to yellow-green range when it binds to amyloid fibrils. The dye interacts with the cross-beta sheet structure of amyloid, which restricts its molecular rotation and dramatically increases its fluorescence. With blue excitation (about 440–450 nm), the emitted light peaks around 482 nm, which falls in the blue-green region and appears as yellow-green to the observer. That’s why the correct color for amyloid using this method is yellow to yellow-green. Red, blue, or magenta would not match the emission characteristics of Thioflavin T bound to amyloid fibrils.