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Metal Ion Effects on the cis / trans Isomerization Equilibrium of Proline in Short‐Chain Peptides: A Solution NMR Study
Author(s) -
Gaggelli Elena,
D'Amelio Nicola,
Gaggelli Nicola,
Valensin Gianni
Publication year - 2001
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/1439-7633(20010803)2:7/8<524::aid-cbic524>3.0.co;2-p
Subject(s) - tetrapeptide , chemistry , isomerization , metal , conformational isomerism , metal ions in aqueous solution , copper , nuclear magnetic resonance spectroscopy , stereochemistry , ion , paramagnetism , crystallography , peptide , molecule , organic chemistry , catalysis , biochemistry , physics , quantum mechanics
Abstract The effect of copper( II ) ions on the probabilities of existence of the four detectable conformers of the tetrapeptide Tyr‐Pro‐Phe‐Pro (β‐casomorphin 4) in [ 2 H 6 ]DMSO was investigated by 1 H 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 ‐H α 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.