Papers by Giovanni Micera
Inorganic chemistry, Jan 8, 2015
The speciation of the potential antitumor agent vanadocene dichloride ([Cp2VCl2], abbreviated wit... more The speciation of the potential antitumor agent vanadocene dichloride ([Cp2VCl2], abbreviated with VDC) in the blood plasma was studied by instrumental (EPR, ESI-MS, MS-MS, and electronic absorption spectroscopy) and computational (DFT) methods. The behavior of VDC at pH 7.4 in aqueous solution, the interaction with the most important bioligands of the plasma (oxalate, carbonate, phosphate, lactate, citrate, histidine, and glycine among those with low molecular mass and transferrin and albumin between the proteins) was evaluated. The results suggest that [Cp2VCl2] transforms at physiological pH to [Cp2V(OH)2] and that only oxalate, carbonate, phosphate, and lactate are able to displace the two OH(-) ions to yield [Cp2V(ox)], [Cp2V(CO3)], [Cp2V(lactH-1)], and [Cp2V(HPO4)]. The formation of the adducts with oxalate, carbonate, lactate, and hydrogen phosphate was confirmed also by ESI-MS and MS-MS spectra. The stability order is [Cp2V(ox)] ≫ [Cp2V(CO3)] > [Cp2V(lactH-1)] > [Cp2V(...
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Journal of inorganic biochemistry, Jan 31, 2015
The biotransformation in the plasma and red blood cells of two potential antitumor V(IV)O complex... more The biotransformation in the plasma and red blood cells of two potential antitumor V(IV)O complexes formed by flavonoid ligands (quercetin or que and morin or mor) and their sulfonic derivatives (quercetin-5'-sulfonic acid or que(S) and morin-5'-sulfonic acid or mor(S)) was studied by spectroscopic (EPR, Electron Paramagnetic Resonance) and computational (DFT, Density Functional Theory) methods. Que and que(S) form with V(IV)O stable complexes, and in the systems with apo-transferrin (apo-hTf) and albumin (HSA) VO(que)2 and VO(que(S))2 remain unchanged. VO(mor)2 and VO(mor(S))2 undergo displacement reactions to give the partial formation of (VO)x(HSA) and (VO)(apo-hTf)/(VO)2(apo-hTf); moreover, mor(S) forms with apo-transferrin and albumin mixed species VO-mor(S)-apo-hTf and VO-mor(S)-HSA. In the systems with apo-hTf and HSA anisotropic EPR spectra at room temperature are detected in which the protein is not directly coordinated to V(IV)O(2+) ion. This is explained assuming ...
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Journal of the Chemical Society, Dalton Transactions, 1995
... 425 Oxovanadium(iv) Complexation by Adenosine 5'-Di-and -Tri-phosphate and Nucle... more ... 425 Oxovanadium(iv) Complexation by Adenosine 5'-Di-and -Tri-phosphate and Nucleotide Building Blocks Elisabetta Alberico/ Dorothee Dewaele/ Tamas Kiss * X and Giovanni Micera * A a Department of Chemistry, University of Sassari, Via Vienna 2, 1-07100 Sassari, Italy ...
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Colloids and Surfaces, 1986
ABSTRACT The ESR spectra of air-dried and fully-hydrated gels of aluminium hydroxide exchanged wi... more ABSTRACT The ESR spectra of air-dried and fully-hydrated gels of aluminium hydroxide exchanged with Mn(II) are described. The results substantiate the presence of two adsorbed species: (i) the ‘free’ species which consists of an hydrated cation retaining almost unperturbed mobility compared with that of [Mn(H2O)6]2+ in dilute aqueous solution; and (ii) the ‘bound’ species which consists of an hydrated cation which interacts directly with the surface sites and is subject to motional restriction and/or geometrical distortion. Specifically adsorbed sulphate favours the formation of the ‘bound’ species.
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Journal of the Chemical Society, Dalton Transactions, 1994
ABSTRACT
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Colloids and Surfaces, 1984
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Colloids and Surfaces, 1983
ABSTRACT The complexes formed by polygalacturonic acid (PGA) with Mn2+, Co2+ and Ni2+ were invest... more ABSTRACT The complexes formed by polygalacturonic acid (PGA) with Mn2+, Co2+ and Ni2+ were investigated by potentiometric titration of the polyelectrolyte in presence of varying amounts of metal ions. Formation functions, evaluated from the titration data and analyzed according to the Bjerrum plot method, were interpreted as evidence of: 1) the involvement of two carboxylate groups in the complex formation; 2) very little difference in preference for the binding of all the three ions by PGA. By taking into account Potentiometric and spectroscopic results (the latter reported elsewhere), an outer-sphere electrostatic structure is suggested for all the complexes. The relevance of this type of interaction in soil biochemistry is discussed.
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Colloids and Surfaces, 1988
ABSTRACT The formation of complexes of copper (II) with pyridinedicarboxylic acids (PDC) on the s... more ABSTRACT The formation of complexes of copper (II) with pyridinedicarboxylic acids (PDC) on the surface of aluminium hydroxide, upon adsorption of metal ion and ligands from aqueous solution, has been studied by means of analytical and spectroscopic (ESR, IR and reflectance absorption) measurements. It has been found that, depending on the ligand structure, different complex species may be formed. Particularly, 2,x−PDC (x = 3, 4 or 5) ligands yield complexes, with 1:1 or 1:2 metal-to-ligand ratios, where the ligand binds to the surface through the x-carboxylate group and chelates the metal via the pyridine nitrogen and the 2-carboxylate group. With the 2,6-PDC ligand only one type of surface complex is formed, where the metal ion is in a compressed octahedral environment, being bound to two tridentate ligands, which interact also with the surface through the uncoordinate oxygens. With 3,y-PDC (y = 4 or 5) surface complexes are observed only at high surface ligand concentrations. They are most likely formed by monodentate (N- or O-) coordination of a surface-adsorbed PDC molecule to a metal ion that is also bound to surface groups. As a consequence of the different structures of the surface complexes, the metal adsorption behaviour is strongly ligand dependent.
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Journal of the Chemical Society, Dalton Transactions, 1999
ABSTRACT The complex formation between VIVO and phosphonic derivatives of iminodiacetic (Ida) and... more ABSTRACT The complex formation between VIVO and phosphonic derivatives of iminodiacetic (Ida) and nitrilotriacetic acids (Nta) has been studied by combined application of pH-potentiometric and spectroscopic (EPR and electronic absorption) techniques. Differently from aminomonophosphonates, which are able to bind the metal ion rather weakly forming five-membered chelated rings, the mixed carboxylic–phosphonic and pure phosphonic derivatives of Ida and Nta form chelated systems resulting in very stable complexes mostly of the 1∶1 type. Substitution of CO2– by PO32– increases the stability of the complexes due to the higher basicities of the phosphonic functions. However, the higher spatial requirement of the phosphonate groups and the greater electrostatic repulsion between the dinegative phosphonate arms would mostly compensate this effect. Spectroscopic evidence has been found for a considerable distortion in the geometry of the aminophosphonate complexes. The differences in the observed stability trends between the corresponding copper(II) and VIVO complexes are also discussed.
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Journal of the Chemical Society, Dalton Transactions, 1990
ABSTRACT The formation of a dimeric VOIV–D-galacturonic acid complex in aqueous solution has been... more ABSTRACT The formation of a dimeric VOIV–D-galacturonic acid complex in aqueous solution has been studied by spectroscopic methods, namely e.s.r., electron nuclear double resonance, and electronic absorption. The complex exhibits properties consistent with a metal–metal distance of about 5.0 Å, which is very similar to that found in the well known VOIV–tartrate dimers. The only way to accommodate the metal ions at such a distance and to fit the spectroscopic data is to assume that the ligand co-ordinates to the metal ion through the CO2–, O(4)– and O(3)–, O(2)– donor sets and adopts an open-chain structure which is stabilized by the dimer complex formation.
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Journal of the Chemical Society, Dalton Transactions, 1989
ABSTRACT The 1H electron nuclear double resonance (ENDOR) spectra of the VOIV–D-galacturonic acid... more ABSTRACT The 1H electron nuclear double resonance (ENDOR) spectra of the VOIV–D-galacturonic acid system in aqueous solution have been studied as a function of pH. Couplings between the paramagnetic ion and the protons of ligand or water molecules have been distinguished by comparative examination of the spectra recorded in water and D2O. Comparison of data with results available from potentiometric and other spectroscopic measurements allowed interpretation of the pH dependence of ENDOR spectra and the assignment of the main observed resonances, e.g. those due to methine protons on the carbon atoms bearing deprotonated carboxyl and/or hydroxyl groups co-ordinated to the metal ion.
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Journal of the Chemical Society, Dalton Transactions, 1990
ABSTRACT The interaction of oxovanadium(IV) with ligands containing phenolate and carboxylate don... more ABSTRACT The interaction of oxovanadium(IV) with ligands containing phenolate and carboxylate donors, such as salicylic acid, catechol, 2,x-dihydroxybenzoic acids (x= 3–6), and 3,4-dihydroxybenzoic acid has been studied in aqueous solution by means of potentiometric and spectroscopic (electronic absorption, e.s.r., and electron nuclear double resonance) techniques. Over the low pH range the salicyclic acid-type mode of co-ordination predominates, while the catechol type is preferred in basic media. A mixture of these donor sets is observed in the ternary oxovanadium(IV)–salicylic acid-catechol and binary oxovanadium(IV)-2,3-dihydroxybenzoic acid systems. Besides monomeric complexes, dinuclear species are also formed by the potentially ambidentate dihydroxybenzoic acid derivatives over the intermediate pH range. In the latter complexes both CO2– and O– groups take part in metal bridging.
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Talanta, 1998
The complex formation between Cu(II) and dl-willardiine [1-(2-amino-2-carboxyethyl)uracil], an an... more 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.
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Biomedica biochimica acta, 1990
Hydroxyl radical generation by living human granulocytes was determined by ESR using DMPO as a sp... more Hydroxyl radical generation by living human granulocytes was determined by ESR using DMPO as a spin trapping reagent. The influence of dihydralazine and exogenous superoxide dismutase (SOD) on the radical generation was observed. In the presence of dihydralazine the radical production increases distinctly; the higher hydroxyl radical production is observed for the dihydralazine-SOD containing system which is explained by the partial decomposition of the enzyme in the presence of dihydralazine. No effect of dihydralazine on the lipid fluidity of the granulocyte membrane and phase transition in the membrane of living granulocytes was observed.
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Copper(II) complexes of oligopeptides with protected amino groups (Z-His-OH, Z-HisGly-OH, Z-GlyHi... more Copper(II) complexes of oligopeptides with protected amino groups (Z-His-OH, Z-HisGly-OH, Z-GlyHis-OH and Z-GlyGlyHis-OH) were studied by potentiometric and spectroscopic methods. The involvement of the imidazole nitrogen in metal binding was proved in slightly acidic media. The deprotonation and coordination of the amide nitrogen atoms from the carbamate or peptide CONH moieties occurred around pH 7, which resulted in the formation
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The system formed by Cu (II) and 2, 2′-bipyridine (bpy) has been revisited by use of EPR and elec... more The system formed by Cu (II) and 2, 2′-bipyridine (bpy) has been revisited by use of EPR and electronic absorption spectroscopies. The mono-chelated [Cu (bpy)] 2+, bis-chelated trans-[Cu (bpy) 2] 2+ with pseudo-tetrahedral geometry due to the steric hindrance of the 3 ...
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Polyhedron, 2001
Copper(II) complexes of the tripeptides GlyGly-β-Ala, Gly-β-AlaGly, β-AlaGlyGly, Gly-β-Ala-β-Ala,... more Copper(II) complexes of the tripeptides GlyGly-β-Ala, Gly-β-AlaGly, β-AlaGlyGly, Gly-β-Ala-β-Ala, β-AlaGly-β-Ala, β-Ala-β-Ala-β-Ala and the tetrapeptides GlyGlyGly-β-Ala, GlyGly-β-AlaGly, Gly-β-AlaGlyGly and β-AlaGlyGlyGly were studied by potentiometric, EPR and UV–Vis spectroscopic methods. The stoichiometry of the complexes of peptides containing β-alanine residues are very similar to those of oligoglycines; [CuL]+, [CuL2], [CuH−1L], [CuH−2L]−, [CuH−1L2]− and [CuH−3L]2− were detected as the major species in all
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Papers by Giovanni Micera