Reactions for Distinguishing Ribo- and Deoxyribonucleic Acids

Colour Reactions for Distinguishing Ribo- and Deoxyribonucleic Acids 

The biuret reaction [alkaline Cu(II)] and the arginine test [102] are used to detect peptides in nucleic acid preparations. Two other colour reactions permit either type of nucleic acid to be detected in the presence of the other one is due to Dische and the other is the phloroglucinol test of v. Etjler and Hahn. 

Procedure A solution of 50—500 (xg nucleic acid in 1 ml water is heated 10 min at 100° C with 2 ml of a solution of 1 g diphenylamine and 2.75 ml cone, sulphuric acid in 100 ml acetic acid. The solution turns blue (abs. max. 595 nm) if deoxyribonucleic acid is present. The difficultly hydrolysable pyrimidine-deoxyribonucleosides and -nucleotides do not react under these conditions. 

Procedure A sample containing about 2 mg ribonucleic acid per ml is heated on the water bath for 50 min with 8 ml of a 0.1% solution of ferric chloride in cone, hydrochloric acid-acetic acid (1 + 6). The reaction mixture is cooled to room temperature and 1 ml of a 25% solution of phloroglucinol in cone, hydrochloric acid-acetic acid-water (25 + 50 + 25) is added. After standing 20 min, the mixture is heated 4 min on the water bath. The colour (abs-max. 680 nm) attains maximum intensity after about 10 h at room temperature. Deoxyribonucleic acid yields no colour. 

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