L-mimosine: an amino acid with maltol-type binding properties toward copper(II), oxovanadium(IV) and other metal ions

The complex formation between -mimosine, α-amino-β-(3-hydroxy-4-oxo-1,4-dihydropyridin-1-yl)-propanoic acid, a rare α-amino acid provided with a 3-hydroxypyridin-4(1H)one moiety, and some metal ions — Cu(II), VO(IV), Ni(II) and Zn(II) — was studied by spectroscopic (EPR and electron absorption) and potentiometric techniques in aqueous solution. It was found that -mimosine prefers the maltol-like donor set of the 3-hydroxypyridin-4(1H)one fragment for binding copper(II) and oxovanadium(IV). However, the presence of two alternative donor centres in the ligand, (COO-, NH2) and (CO, O-), both suitable for chelating behaviour, makes possible the formation of very stable polynuclear species in which the -mimosine ligand coordinates at both the (CO, O-) maltol-like and the (COO-, NH2) α-aminocarboxylate sites. Nickel(II) interacts with the ligand, but prefers a mixed bonding mode in the bis chelated species. Zn(II) only forms complexes with the 3-hydroxypyridin-4(1H)one fragment

Coordination ability of selected amino sugars with Cu²⁺ ions in solution

Complex formation between Cu(II) and the amino sugars methylβ-L-daunosaminide (MeDauN), 6-amino-6-deoxy-D-glucose (Glc6N), 3-dimethylamino-3,4,6-trideoxy-D-xyloheksose (desosamine DSA), and methyl-3-amino-3-deoxy-α-D-mannopyranose (MeMan3N) was studied in aqueous solution by potentiometric and spectroscopic (EPR, electron absorption, and CD) techniques. The results show that Glc6N and DSA ligands, lacking the cis-oriented couples of [NH2, OH] donors, give rise only to dimeric complexes. The other two ligands, although both forming mononuclear species, exhibit different coordination abilities, depending on the assistance of donors able to yield axial interaction with the metal ion

Co-ordination ability of Cu²⁺ ion toward the nucleobase-amino acid willardiine

The complex formation between CuII 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 α-amino-carboxylate chelating set. The uracil moiety, however, can coordinate the metal ion in basic solution giving rise to intermolecular bridging

Copper(II) complexes of (<i>R</i>,<i>S</i>)-alpha-hydroxymethylornithine and its N^delta-benzoyl derivative

Complex formation between copper(II) and (R,S)-α-hydroxymethylornithine of (R,S)-Nα-benzoyl-α-hydroxymethylornithine was studied in aqueous solution by potentiometric and spectroscopic (electron paramagnetic resonance and electronic absorption) techniques. The results show that the α-hydroxymethyl derivatives of ornithine are coordinated through the alcoholic group to the copper(II) ion in basic solution. Deprotonation and coordination of the α-hydroxymethyl group occurs and yields species with the amino and/or carboxylato groups also bound to the metal ion

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

Complex formation between Cu(II) and human and bovine β-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. The presence of two additional hydrophobic residues on the C-terminal makes heptapeptide molecule much more effective ligand than its pentapeptide N-terminal fragment