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V. G. Badelin, E. Y. Tyunina, I. N. Mezhevoi

Author affiliations
G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences
Akademicheskaya str., 1, 153045 Ivanovo, Russia
E-mail: tey@isc-ras.ru

Abstract
Aromatic α-amino acids (L-phenylalanine, L-tyrosine, L-tryptophan) and aliphatic peptides (glycyl-glycine, triglycine, β-alanyl-glycine, β-alanyl-β-alanine, glycyl-DL-alanine, DL-alanyl-glycine, L-alanyl-L-alanine, DL-alanyl-DL-alanine, DL-alanyl-DL-valine) were investigated by methods of thermogravimetry (TG) and differential thermal analysis (TGA) in temperature ranges 50–700 ^oС and 50–450 ^oС, correspondingly. The thermal degradation of the substances was studied. It has been shown that the differences in the spatial structure of the solid amino acids and aliphatic peptides have an influence on the character of phase transformations.The characteristics of thermal destruction stages were defined. The thermal stability of the amino acids with aromatic rings in the side chain structure was higher than the aliphatic amino acids. For two linear dipeptides (β-alanyl-glycine and β-alanyl-β-alanine), the melting process is accompanied by chemical decomposition. Melting stage does not occur on heating of other dipeptides. The tendency of the decomposition temperature increase with the increase of heat capacities of crystalline amino acids and peptides is established.

Keywords: aromatic amino acids, aliphatic peptides, thermal stability, thermogravimetry, differential thermal analysis