Synthesis and spectroscopic characterization of ternary complexes of copper(II) glycylglycine and substituted phenanthrolines

Complexes of Cu(glygly)phen {glygly =glycylglycine; phen=4,7-dimethyl [(1)], 5,6-dimethyl [(2)], 5-NO2[(3)], 5-Cl[(4)], 2-oxazolinyl (2-ox) [(5)] phenanthroline} and bis(2-oxazolinylphenanthroline)copper(II) [(6)] were synthesized and characterized by conductivity measurements, e.p.r., i.r. and reflectance electronic spectroscopies. A broad u.v.-vis. band in the 620-640 nm range and a shoulder at ca. 825 nm suggest that these complexes are five-coordinate. The e.p.r. spectra indicate a stronger equatorial ligand field in the ternary complexes which is absent in the binary Cu-phen complexes, suggesting square pyramidal coordination, whose base contains the three donor atoms from glygly (O, N, N) and one donor from the phenanthroline nitrogen atom. The other nitrogen-containing ligand of the phenanthroline is in an apical position. The spectroscopic results can be correlated with electronic and steric effects attributable to the different substituents on the phenanthroline ligands. Only small variations in the structure of the ternary complexes occur as a function of the electronic effects of substituents on the aromatic phenanthroline ring ligands. Steric hindrance predominates in determining coordination geometry around copper(II)

Electron Paramagnetic Resonance Study of Retention of Chromium(III), Chromate or Dichromate(VI) and Copper(II) ions by Thermotolerant Hansenula polymorpha

We report on CrIII and CrVI interaction with Hansenula polymorpha, a thermotolerant yeast, studied by means of EPR spectroscopy at room temperature. CrIII retention results in a reduced mobility of the ion, probably due to the formation of complexes immobilized on a polymeric matrix of cell. CrVI interaction produces stable, mobile CrV species, which can eventually partially decay to CrIII species. Different reducing agents in the cell may be responsible for this behaviour, especially on cell wall components or on cytoplasmic space. A comparison with a previous study on CuII ion retention is also made

Park9 interaction with Manganese and other divalent cations

Two peptide sequences from Park9 Parkinson’s disease gene, P1D2E3K4H5E6L7 (1) and F1C2G3D4G5A6N7D8C9G10 (2) have been studied in their interaction with Mn(II) and Zn(II) ions. These fragments lie from residue 1165 to 1171 and from 1184 to 1193 in the Park9 encoded protein, that can protect cells from manganese poisoning, an environmental risk factor for a Parkinson’s disease-like syndrome called Manganism. The study was carried out through potentiometric and spectroscopic (UV-Vis, EPR, mono- and multidimensional NMR) techniques, to cast light on the details of metal binding at different pH values and different ligand to metal molar ratios

Interaction of divalent cations with peptide fragments from Parkinson’s disease genes

Protected Ac-PDEKHEL-NH2 (PK9-H) and Ac-FCGDGANDCG-NH2 (PK9-C) peptide fragments corresponding to sequences from residues 1165 to 1171 and 1184 to 1193, respectively, in the Park9 encoded protein from Parkinson’s disease gene, were tested for their protonation and complex formation capabilities with Cu(II), Zn(II) and Mn(II) ions by potentiometric and UV-Vis measurements. The effects of peptide titration with the metal ions have been followed by mono- and bi-dimensional NMR spectroscopy in order to support the potentiometric results and to understand the details of metal binding. Only mononuclear complexes have been evidenced for all the checked metal ions with PH9-H peptide. Mononuclear and bis-complexes with PK9-C peptide have been evidenced with Cu(II) and Zn(II) metal ions. From the dissociation-constants and pM values obtained for the binary competition diagrams for the systems containing Cu(II), Zn(II) or Mn(II) and the two ligands, Cu(II) ion is able of binding more efficiently than Zn(II) and Mn(II) metal ions to both ligands

EPR Study on Vanadyl and Vanadate Ion Retention by a Thermotolerant Yeast

The retention of vanadyl(IV) and vanadate(V) ions by Hansenula polymorpha, a thermotolerant yeast, has been studied by EPR spectroscopy. Vanadyl ions were retained as mobile complexes associated with relatively low molecular weight ligands as well as immobilized complexes formed with high molecular weight residues, the donor atoms of which are probably oxygens or deprotonated hydroxyls. The distribution of vanadyl ions between mobile and immobilized complex species is a function of the metal concentration as well as of the contact time. Vanadate ions were reduced by cellular components to vanadyl ions