Model investigations for vanadium-protein interactions: vanadium(III) compounds with dipeptides and their oxovanadium(IV) analogues

 
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Model investigations for vanadium-protein interactions: vanadium(III) compounds with dipeptides and their oxovanadium(IV) analogues (EN)

Tasiopoulos, A. J. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Tasiopoulos, A. J. (EN)

The reaction of VCl3 with 1,10-phenanthroline and a series of dipeptides (H(2)dip), having aliphatic as well as aromatic side chains, in methyl alcohol and in the presence of triethylamine affords vanadium(III) compounds of the general formula [V-III(dip)(MeOH) (phen)]Cl. Aerial oxidation/hydrolysis of the vanadium(III) species gives their oxovanadium(IV) analogues of the general formula [(VO)-O-IV(dip)(phen)] X-ray crystallographic characterization of the [(VO)-O-IV(dip)(phen)] compounds (where dip(2-) = Gly-L-Ala, Gly-L-Val and Gly-L-Phe) revealed that the vanadium atom possesses a severely distorted octahedral coordination and is ligated to a tridentate dip(2-) ligand at the N-amine atom, the deprotonated N-peptide atom and one of the O-carboxylate atoms, as well as an oxo group and two phenanthroline nitrogen atoms. Circular dichroism characterization of the V-III/(VO2+)-O-IV-dipeptide compounds revealed a strong signal for the (VO2+)-O-IV species in the visible range of the spectrum, with a characteristic pattern which may be exploited to identify the N-am, N-pep and O-car ligation of a peptide or a protein to (VO2+)-O-IV center, and a weak Cotton effect of opposite sign to their vanadium(III) analogues. The visible spectra of the V-III-dipeptide compounds revealed two d-d bands with high intensity, thus indicating that the covalency of the metal-donor atoms is significant, i.e. the vanadium d orbitals are significantly mixed with the ligand orbitals, and this is confirmed by the low values of their Racah B parameters. The high-intensity band of the (VO2+)-O-IV-dipeptide compounds at similar to460 nm implies also a strong covalency of the metal with the equatorial donor atoms and this was supported by the EPR spectra of these compounds. Moreover, the V-III/(VO2+)-O-IV-dipeptide complexes were characterized by EPR and IR spectroscopies as well as conductivity and magnetic susceptibility measurements. (EN)

vanadium (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Journal of Biological Inorganic Chemistry (EN)

Αγγλική γλώσσα

2002

<Go to ISI>://000174957800002

Springer Verlag (Germany) (EN)



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