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Updated: Oct 2, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Metal ion effects on the cis/trans isomerization equilibrium of proline in short-chain peptides: a solution NMR study
E Gaggelli1, N D'Amelio, N Gaggelli
1Department of Chemistry and NMR Center, University of Siena, Via A. Moro, Siena 53100, Italy.
Abstract:
The effect of copper(II) ions on the probabilities of existence of the four detectable conformers of the tetrapeptide Tyr-Pro-Phe-Pro (beta-casomorphin 4) in [2H6]DMSO was investigated by 1H NMR spectroscopy. Integration of the Phe-NH signals provided the relative populations in the free state as tt/tc/ct/cc=28:34:29:9 at 293 K (c=cis, t=trans). Copper(II) was shown to bind to all four isomers, yielding complexes with two different structures, depending on the conformation of Pro(2). The interpretation of paramagnetic relaxation rates of Pro(2)-Halpha signals provided the corresponding isomeric probabilities in the metal-bound state as 13:36:20:31. The observed stabilization of the conformation with the lowest probability of existence (cc) may be relevant for the biological role of copper and other metal ions.
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