Nuclear magnetic resonance studies of exchangeable protons. II. The solvent exchange rate of the indole nitrogen proton of tryptophan derivatives
✍ Scribed by Susan F. Waelder; Alfred G. Redfield
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1977
- Tongue
- English
- Weight
- 376 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
The exchange rate of the indole nitrogen proton with solvent water protons was measured as a function of pH and temperature for tryptophan, N‐methyl tryptophan, glycyl tryptophan, tryptophanamide, tryptophylglycine, and tryptophylglycyl glycine. The nmr observation was by long‐pulse Fourier transform methods, and kinetics were inferred from saturation recovery, H~2~O transfer of saturation, and linewidth. There are observable differences between the rates of these compounds, but all are describable within a factor of two by specific acid and base‐catalyzed rates k~H~ = 100 and k~OH~ = 10^8^ 1/mol‐sec at 27°C. It is concluded that this behaviour is representative of this proton on the indole side chain in a random‐chain peptide exposed to water.