Congo Red

Property Data
Common name
Suggested name
Other names
 
C.I. number
C.I. name
Class
Ionisation
Solubility aqueous
Solubility ethanol
Absorption maximum
 
Colour
Empirical formula
Formula weight
Congo red
Congo red
Direct red
Cotton red
22120
Direct red 28
Azo
Acid
Readily
0.19%
497 (Conn, Aldrich),
488 (Merck), 486 (Gurr)
Red
C32H22N6O6S2Na2
696.7

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.

 

Reference
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

 


 

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