Congo red

The leak turned a tributary of the River Congo red and killed huge numbers of fish, which some people ate, said Environment Minister Eve Bazaiba.

As defined by pathologists1 who document amyloids in numerous diseases, the fibrils must be deposited in body tissues and fluoresce a green–yellow colour when stained with the dye Congo red and viewed between crossed polarizers.

Amyloid is defined pathologically by the demonstration of green birefringence on binding of the dye Congo red and biophysically by a cross-β fibre diffraction pattern. b, Models of recombinant PrP fibrils and ex vivo prions.

Amyloid is defined pathologically by the demonstration of green birefringence on binding of the dye Congo red and biophysically by a cross-β fibre diffraction pattern. b, Models of recombinant PrP fibrils and ex vivo prions.

When doused with Congo red, a standard pathology stain, and illuminated with polarized light, the Alzheimer's plaques — just like scrapie plaques — displayed an apple-green shimmer, a prismatic sign of the hydrogen bonds that held their fibrils tightly together.