Conformer Interconversion in the LC Analysis of Triostin A and Its Under-N-Methylated Synthetic Analogue
| Autor: | August H. Maki, Paul Bruins, Jean-Louis Excoffier, Thomas V. Alfredson |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Magnetic Resonance Spectroscopy
Chloroform Chromatography Bicyclic molecule Elution Kinetics Molecular Conformation General Medicine Activation energy Methylation Anti-Bacterial Agents Analytical Chemistry chemistry.chemical_compound Reaction rate constant chemistry Quinoxalines Yield (chemistry) Spectrophotometry Ultraviolet Conformational isomerism Chromatography Liquid |
| Zdroj: | Journal of Chromatographic Science. 32:132-138 |
| ISSN: | 1945-239X 0021-9665 |
| DOI: | 10.1093/chromsci/32.4.132 |
| Popis: | Multiple peak formation and interconversion in the liquid chromatographic (LC) analysis of triostin A and its under-N-methylated synthetic analogue, [N-MeCys3,N-MeCys7]-TANDEM (MCTANDEM), are investigated as a function of column temperature. Slow interconversion between chromatographic peaks, ascribed to the presence of the n- and p-solution conformers of the peptides, is exhibited in the normal-phase elution profiles of triostin A and in the reversed-phase elution profiles of MCTANDEM. A chromatographic model is developed to estimate the kinetics of conformer interconversion. Reversed-phase LC analysis of the n- and p-conformers of MCTANDEM yields a value of 0.01/s for the apparent interconversion rate constant (kn-p) at 25 degrees C, with a corresponding activation energy of 16 kcal/mol. Normal-phase LC analysis of the n- and p-conformer interconversion of triostin A dissolved in chloroform results in a value of 0.04/s for kn-p at 25 degrees C, with a corresponding activation energy of 18 kcal/mol. For triostin A, normal-phase LC findings as a function of column temperature are compared with 1H nuclear magnetic resonance (NMR) line-width measurements between 80 degrees C and 140 degrees C for the n- and p-conformers, which yield an activation energy of 19 kcal/mol and an extrapolated value of 0.02/s at 25 degrees C for kn-p in deuteriochloroform. |
| Databáze: | OpenAIRE |
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