Co-ordination ability of Cu(2+) ion toward the nucleobase-amino acid willardiine.

The complex formation between Cu(II) and dl-willardiine [1-(2-amino-2-carboxyethyl)uracil], an analog of phenylalanine containing the uracil residue, was investigated by potentiometric and spectral studies. The results indicate that the primary metal binding site of the ligand is the alpha-amino-carboxylate chelating set. The uracil moiety, however, can coordinate the metal ion in basic solution giving rise to intermolecular bridging.

Specific interactions of bovine and human beta-casomorphin-7 with Cu(II) ions.

Complex formation between Cu(II) and human and bovine beta-casomorphin heptapeptides, Tyr-Pro-Phe-Val-Glu-Pro-Ile and Tyr-Pro-Phe-Pro-Gly-Pro-Ile, respectively, was investigated by pH potentiometry and spectroscopic (CD, EPR and electronic absorption) techniques. The results showed the critical impact of Pro residues on the complex equilibria formed. The presence of the Pro residue at the second position leads to formation of very stable dimeric species in which two metal ions co-ordinate to N-terminal ¿NH2, C=O¿ binding sites of one peptide molecule and the deprotonated phenolic oxygen of the second ligand molecule.

Binding ability of Cu2+ ions by opiate-like fragments of bovine casein.

The coordination modes of Cu(II) to alpha-casein (90-95) and alpha-casein (90-96) peptides with opioid activity isolated from pepsin hydrolisates of alpha-casein were investigated by means of electron paramagnetic resonance, absorption, and circular dichroism spectroscopy and potentiometry. The results allow the identification of the complex species involved and the attribution of the spectral data set to the various complex structures. According to the spectroscopic data, a phenolate side-chain of Tyr residue belonging to the Gly-Tyr-Leu or Gly-Tyr-Leu-Gln fragment of the peptides is involved in the metal coordination in a complex which is a minor species at neutral pH range.