Intramolecular H-bonds and thioamide rotational isomerism in thiopeptides
| Autor: | Péter Sándor, Emma Kollát, Gyula Batta, Zsuzsa Majer, Miklós Hollósi, Medhen Zewdu, Katalin E. Kövér, Márton Kajtár |
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| Rok vydání: | 2009 |
| Předmět: |
chemistry.chemical_classification
Magnetic Resonance Spectroscopy Dipeptide Protein Conformation Hydrogen bond Stereochemistry Chemical shift Hydrogen Bonding Dipeptides Nuclear magnetic resonance spectroscopy Biochemistry Thioamides chemistry.chemical_compound Isomerism chemistry Intramolecular force Side chain Molecule Thioamide |
| Zdroj: | International Journal of Peptide and Protein Research. 36:173-181 |
| ISSN: | 0367-8377 |
| Popis: | Mono- and dithionated N-acyl amino acid and dipeptide N'-methylamides were synthesized using Lawesson's reagent and S-thioacetyl thioglycolic acid. The conformation of the thionated models was characterized by IR, 13C, and 1H NMR spectroscopy, including NOE experiments. The formation of -C = S...H-N-C = X (X = O or S) intramolecular H-bonds of the type 2----2, 1----3 and 1----4 was evidenced by the characteristic shifts of the IR stretching frequencies of the NH group. Act-Pro-NHCH3(4) and Act-Prot-NHCH3(5) were found to be present as mixtures of rotational isomers about the CS-N bond. 13C chemical shifts of the gamma- and beta-carbons of the proline ring elucidated the conformation (Z or E) of the tertiary thioamide group. Our results suggest that the conformation of thiopeptides is determined by two factors: 1) the H-bond donating and accepting ability of the thioamide group and 2) the repulsion between the thiocarbonyl sulfur atom and the side chain groups of the neighbouring amino acid residues. |
| Databáze: | OpenAIRE |
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