Acid and Alkaline Degradation of the TNP-Amino Acids and -Peptides

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Abstract
Most of TNP-amino acids could be hydrolyzed with N sodium hydroxide at room temperature and gave picric acid and the corresponding free amino acids quantitatively. However, TNP-glycine, -serine and -threonine were decomposed into unidentified colored substances, without producing an appreciable amount of picric acid and free amino acids. TNP-Amino acids were rather stable in acid. For example, no appreciable amount of TNP-valine was hydrolyzed with 6 N hydrochloric acid, and more than 80 per cent remained intact even with 12 N acid, after the treatment for 72 hours at 37°C. TNP-α-NH linkage of TNP-amino acids and -peptides, however, was cleaved quantitatively into picric acid and original free amino acids by heating with 6 N hydrochloric acid at 110°C or 8 to 10 hours. TNP-ω-NH linkages were rather resistant to the conditions, and more than 60 per cent were capable of remaining intact even after the prolonged heating for 24 hours in 6 N hydrochloric acid. Extreme stability of TNP-amines in acid was also observed. Analysis of TNP-peptides produced by the partial acid or enzymatic hydrolysis of TNP-protein was described. Amino acid contents of these TNP-peptides were able to be represented as the relative ratios to the contents of picric acid, liberated.