Characterization of symmetrical and unsymmetrical thiol–disulfide interchange reactions by one-and two-dimensional magnetization transfer NMR spectroscopy
✍ Scribed by David A. Keire; Wei Guo; Dallas L. Rabenstein
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 730 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
Abstract
One‐ and two‐dimensional magnetization transfer NMR methods were used to characterize symmetrical and unsymmetrical thiol–disulfide interchange reactions in the glutathione‐cysteamine system. The chemical system consists of four symmetrical and two unsymmetrical thiol–disulfide interchange reactions. In terms of the magnetization transfer experiment, these reactions can be treated as two three‐site exchange networks, one for exchange of the cysteamine moiety among cysteamine, cystamine and the cysteamine part of the glutathione–cysteamine mixed disulfide and another for exchange of the glutathione moiety among glutathione, glutathione disulfide and the glutathione part of the mixed disulfide. Two‐dimensional ^13^C{^1^H} EXSY NMR spectroscopy was used to identify specific exchange reactions which take place on the time scale of the magnetization transfer experiment at a given pD. The kinetics of the interchange reactions were quantitatively characterized using an overdetermined version of the one‐dimensional ^13^C{^1^H} EXSY experiment and a ^13^C{^1^H} selective inversion‐transfer experiment with a linear‐least‐squares analysis of the time course data. Second‐order rate constants were calculated for all six of the thiol–disulfide interchange reactions from the pseudo‐first‐order rate constants obtained from the selective inversion‐transfer experiments.