13C-nuclear magnetic resonance study of [85% 13C-enriched proline]thyrotropin releasing factor: 13C-13C vicinal coupling constants and conformation of the proline residue.
- 1 December 1975
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 72 (12), 4948-4952
- https://doi.org/10.1073/pnas.72.12.4948
Abstract
To understand fully interactions between peptides and cellular receptors, peptide side chain conformation must be defined. In many cases the complexity of proton NMR prevents this, but the present work demonstrates this problem can be solved by using 13C enrichment. Selective 13C enrichment of a natural peptide hormone was achieved by preparing [85% 13C-enriched proline]thyrotropin releasing factor which was examined by 13C NMR spectroscopy at various pH values. Because of the 13C enrichment, 1-bonded and 3-bonded (vicinal) 13C-13C coupling constants were determined. The latter vary from 0-5 Hz and show bond angle dependence. In this hormone the pyrrolidine ring is not free but fixed in the C.gamma.-endo puckered conformation. It has also been possible to assign chemical shift values for a second order 13C NMR spectrum.Keywords
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