Congo red is used to stain amyloid, and is considered the reference standard for the purpose. It is believed that it hydrogen bonds to the beta pleated sheet structure of amyloid with the dye molecules aligned in a very regular manner. This forms a "pseudocrystal", which results in a characteristic, green birefringence of the stained amyloid.
Compare this dye to other direct cotton dyes for amyloid.
R. D. Lillie.
Conn's Biological Stains
Williams & Wilkins, Baltimore, MD., U.S.A.
Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.
Aldrich chemical catalogue, 1992
Aldrich Chemical Company, Milwaukee, WI, USA.
Susan Budavari, Editor, (1996)
The Merck Index, Ed. 12
Merck & Co., Inc., Whitehouse Station, NJ, USA