Feulgen Reaction

Feulgen reaction [′fȯil·gən rē‚ak·shən]

(analytical chemistry)

An aldehyde specific reaction based on the formation of a purple-colored compound when aldehydes react with fuchsin-sulfuric acid; deoxyribonucleic acid gives this reaction after removal of its purine bases by acid hydrolysis; used as a nuclear stain.

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Feulgen Reaction 

a means for the histochemical detection of deoxyribonucleic acid (DNA) in animal and plant cells, as well as in bacteria. It was proposed in 1924 by the German chemist R. Feulgen.

The Feulgen reaction consists of two steps. Initially, acid hydrolysis is performed, usually for 8–12 min, resulting in the cleavage of the nitrogen bases and formation of aldehyde groups. The preparations are then placed in light yellow Schiff reagent (fuchsine-sulfurous acid), which forms bonds with these groups. The red-violet product formed in this step is evidence of the presence of DNA. The Feulgen reaction can be carried out after the use of any fixative (with the exception of Bouin’s fluid, which contains picric acid). The Feulgen reaction is used for the quantitative determination of DNA. Various modifications of the reaction exist for determining the location and structure of DNA with the aid of electron microscopes.