SMS 201–995, a very potent analogue of somatostatin. Assignment of the 1H 500 MHz n.m.r. spectra and conformational analysis in aqueous solution
- 31 May 1985
- journal article
- research article
- Published by Wiley in International Journal of Peptide and Protein Research
- Vol. 25 (6) , 608-614
- https://doi.org/10.1111/j.1399-3011.1985.tb02217.x
Abstract
The conformations of a cyclic analog of somatostatin SMS 210-995, were studied by NMR spectroscopy at 500 MHz in aqueous solution. Assignments were made by use of 2D-correlated methods especially by detecting long-range connectivities in order to identify the aromatic amino acid and long-range couplings between .alpha. protons of consecutive residues. Measurements of temperature coefficients of amide protons and of NH-.alpha.H coupling constants concluded that in water the molecule is rather flexible, with no evidence for a .beta. turn structure involving Thr6. An equlibrium involving 2 .gamma. turn conformations stabilized respectively by Cys2-D-Trp4 and Phe3-Lys5 hydrogen bounds, is responsible for the large upfield shift observed for the Lys5 .gamma. protons and is compatible with the measured JNH-C.alpha.H coupling constants.Keywords
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