The kinetics of hydrazinolysis of simple peptides in anhydrous hydrazine

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Abstract
The kinetics of the uncatalyzed and acid-catalyzed hydrazinolysis of 5 simple peptides was studied by an experimental technique involving hydrazinolysis, treatment with benzaldehyde, dinitrophenylation and paper chromatography. First-order rate constants were obtained for the uncatalyzed reaction and also for the catalyzed hydrazinolysis in the presence of a large excess of catalyst. In [image]-hydrazine sulfate at 60[degree] the reaction is about 5 times as fast as in anhydrous hydrazine. On the basis of the rate constants it is possible to make recommendations about the use of the hydrazine method for the determination of the C-terminal amino acids of proteins. The energies and entropies of activation calculated for 2 peptides show that the approximately 1000-fold range of rate constants encountered in the catalyzed hydrazinolysis at 60[degree] is due largely to steric effects. This may allow selective hydrazinolysis of peptide bonds in proteins.