Biomedical subjects

D Sanna

Publications and source records attributed to D Sanna.

8 recordsLinked to original sources

PubMed2000

The effect of histidyl residues on the complexation of bis(imidazolyl) containing tripeptides with copper(II) ion.

Copper(II) complexes of tripeptide derivatives of bis(imidazol-2-yl) group have been studied by potentiometric, UV-visible and EPR spectroscopic methods. The peptide molecules correspond to the amino acid sequence of collagen containing histidyl residues in different locations and were connected to the bis(imidazol-2-yl) group either on the C-termini (BOC-Pro-Leu-His-BIMA, BOC-His-Leu-Gly-BIMA) or on the N-termini (BIP-His-Ala-Gly-OEt, BIP-Ile-Ala-His-OMe). It was concluded that the imidazole nitrogen donor atoms of the bis(imidazol-2-yl) moiety are the primary metal binding sites, but the histidyl imidazole nitrogens in the side chains have also some effect on the stability and the coordination mode of the complexes. All ligands can coordinate tridentately to copper(II) ion forming a six-membered chelate and a macrochelate in the [CuL]2+ complexes, which results in a slight distortion in the coordination geometry of [CuL2]2+ complexes. The deprotonation and coordination of amide nitrogens, however, were not observed in any cases.

Binding Sites↗

PubMed2000

Can the 1,5-disubstituted tetrazole ring modify the co-ordinating ability and biological activity of opiate-like peptides?

The copper(II) complexing ability and the biological activity of beta-casomorphin-7 tetrazole analogues have been investigated. Potentiometric and spectroscopic (UV-Vis, CD and EPR) studies have been used to establish the thermodynamic stability, speciation and structure of Cu(II) complexes with YP-psi(CN4)-FPGPI-NH2 (1), YPF-psi(CN4)-AGPI-NH2 (2) and YPFP-psi(CN4)-GPI-NH2 (3). Comparison of the binding ability of the tetrazole analogues reveals that the most effective ligand for copper(II) is YPF-psi(CN4)-AGPI-NH2. The effectiveness of this ligand comes from its particular conformation suited for the Cu(II) 2N co-ordination mode in the physiological pH region. The ability of casomorphin tetrazole analogues to activate rat mast cells to histamine release in vitro in the presence of copper(II) has been studied.

Animals↗

PubMed1999

Effect of the tetrazole cis-amide bond surrogate on the complexing ability of some enkephalin analogues toward Cu(II) ions.

A study of the effect of the tetrazole moiety, a cis-amide bond surrogate, on the Cu(II) coordinating properties of oligopeptides is reported. The insertion of the tetrazole moiety psi (CN4) into the peptide sequence of [Leu5]enkephalin considerably changes the coordination ability of the ligand. Potentiometric and spectroscopic results indicate that if the tetrazole moiety is in a suitable position in the peptide chain, i.e. if it follows the third residue, an unusual stable CuH-1L species involving 4N coordination is formed in the physiological pH region. The tetrazole psi (CN4) ring provides one of these nitrogens. The data indicate that Cu(II) ions are strongly trapped inside a bent peptide backbone. However, the coordination mode involving the tetrazole ring nitrogen does not prevent the hydrolysis process under strongly basic conditions.

Amino Acid Sequence↗

PubMed1998

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. The presence of two additional hydrophobic residues on the C-terminal makes heptapeptide molecule much more effective ligand than its pentapeptide N-terminal fragment.

Animals↗

PubMed1998

Copper(II) Complexes of Opiate-like Food Peptides.

The alpha-casein peptide fragment (90-96) Arg-Tyr-Leu-Gly-Tyr-Leu-Glu, one of the exorphins called "food hormones", is an efficient ligand for Cu(II) ions. Potentiometric and spectroscopic studies on aqueous solutions indicate that, depending on the pH range, complex species with different coordination modes (involving the amino and the deprotonated amide groups) are formed. The phenolate side chain of the Tyr residue is not involved in the metal coordination.

Journal Article↗

PubMed1995

Potentiometric and spectroscopic studies on the copper(II) complexes of peptide hormones containing disulfide bridges.

Copper(II) complexes of oxytocin, 4-Glu-oxytocin, 5-Asp-oxytocin, and GlyGlyGly-Lys8-vasopressin were studied by potentiometric, EPR, and UV-visible spectroscopic methods. The formation of 4N-coordinated complexes was characteristic of all ligands. This type of coordination is especially favored for oxytocin due to the specific conformation of the ring coupled by the disulfide bridge. The coordination of the gamma-carboxylate group of 4-Glu-oxytocin and a disulfide sulfur atom of GlyGlyGly-Lys8-vasopressin was reported to occur in the 2N-complexes over medium pH range.

Amino Acid Sequence↗

PubMed1993

EPR investigation of the oxovanadium(IV) complexes formed by the tripeptide glutathione and some related ligands in aqueous solution.

Complex formation between oxovanadium(IV) and glutathione (gamma-L-glutamyl-L-cysteinylglycine, GSH) was investigated in aqueous solution by EPR and electron absorption spectroscopy to identify the complexed species that were reported to form upon reduction of exogenous vanadium(V) in cellular systems. The complexing behavior of the related ligands glycine, N-acetyl-glycine, 3-mercaptopropionic acid, cysteamine, L-cysteine, N-acetyl-L-cysteine, N-acetyl-cysteamine, and oxidized glutathione (GSSG) was also examined in order to have suitable reference models. The results are compared with those reported previously.

Amino Acid Sequence↗

PubMed1992

Oxovanadium(IV) complex formation by simple sugars in aqueous solution.

The binding of oxovanadium(IV) to simple sugars in neutral or basic aqueous solution, as studied by EPR and electronic absorption spectroscopy, is reported. The complexation is favored in basic media and involves the coordination of the metal ion to couples of adjacent deprotonated hydroxyls of the sugar molecule. However, only the ligands provided with cis couples can adopt this chelating ligand behavior. The ability of the cis hydroxyl couples to yield chelated complexes has been related to the structural rearrangement (decrease of the O-C-C-O torsion angle in the five-membered chelated ring) needed to permit the oxovanadium(IV) coordination by the sugar molecule.

Carbohydrates↗