Luigi Casella

University of Pavia, Ticinum, Lombardy, Italy

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Publications (198)652.69 Total impact

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    ABSTRACT: Parkinson’s disease (PD) is a neurodegenerative disorder characterized by the presence of abnormal α-synuclein (αS) deposits in the brain. Alterations in homeostasis and metal-induced oxidative stress may play a crucial role in the progression of αS amyloid assembly and pathogenesis of PD. Contrary to αS, β-synuclein (βS) is not involved in the PD etiology. However, it has been suggested that the βS/αS ratio is altered in PD, indicating that a correct balance of these two proteins is implicated in the inhibition of αS aggregation. αS and βS share similar abilities to coordinate Cu(II). In this study, we investigated and compared the interaction of Cu(I) with the N-terminal portion of βS and αS by means of NMR, circular dichroism, and X-ray absorption spectroscopies. Our data show the importance of M10K mutation, which induces different Cu(I) chemical environments. Coordination modes 3S1O and 2S2O were identified for βS and αS, respectively. These new insights into the bioinorganic chemistry of copper and synuclein proteins are a basis to understand the molecular mechanism by which βS might inhibit αS aggregation.
    Inorganic Chemistry 12/2014; · 4.59 Impact Factor
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    ABSTRACT: At cardiovascular level, nitric oxide (NO) controls smooth muscle functions, maintains vascular integrity and exerts anti-hypertensive effect. Metal-nonoates are a recently discovered class of NO donors, with NO release modulated through the complexation of the N-aminoethylpiperazine N-diazeniumdiolate ligand to metal ions and therefore representing a significant innovation with respect to the drugs traditionally used. In this study, we characterized the vascular protective effects of the most effective compound of this class, Ni(PipNONO)Cl, compared to the commercial NONOate derivate DETA/NO. Ni(PipNONO)Cl induced a concentration dependent relaxation of pre-contracted rat aortic rings. The ED50 was 0.67 μM, compared to 4.3 μM obtained with DETA/NO. When tested on cultured microvascular endothelial cells, Ni(PipNONO)Cl exerted a protective effect on the endothelium, promoting cell proliferation and survival in the range of pM. The administration of Ni(PipNONO)Cl to vascular smooth muscle cells reduced cell number, promoting their apoptosis at high concentration (10 μM). Inhibition of smooth muscle cell migration, a hallmark of atherosclerosis, was accompanied by cytoskeletal rearrangement and loss of lamellipodia. When added to isolated platelets, Ni(PipNONO)Cl significantly reduced ADP induced aggregation. Since atherosclerosis is accompanied by an inflammatory environment, cultured endothelial cells were exposed to interleukin-1 beta (IL-1β). In the presence of IL-1β, Ni(PipNONO)Cl inhibited cyclooxygenase.2 (COX-2) and inducible nitric oxide synthase (iNOS) upregulation, reduced endothelial permeability and the platelet and monocyte adhesion markers CD31 and CD40 at the plasma membrane. Overall, these data indicate that Ni(PipNONO)Cl exerts vascular protective effects relevant for vascular dysfunction and prevention of atherosclerosis and thrombosis.
    Journal of Pharmacology and Experimental Therapeutics 09/2014; · 3.89 Impact Factor
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    ABSTRACT: Inspired by catalytic sites of cytochrome c oxidase (CcO) and nitric oxide reductase (NOR), a new series of dinuclear heme–non-heme complexes is described. The complexes are derived from the association between an iron(III)–protoporphyrin IX containing a covalently attached Gly-L-His-OMe residue to one propionic acid substituent (HMGH) and a metal complex with a tridentate amino-bis(benzimidazole) (BBH) ligand, mimicking the tris-histidine coordination of FeB and CuB in NOR and CcO, respectively. Besides the coordination of FeIII and CuII with the BBH ligand, we also explored the role of “non-biomimetic” metals, such as CoII, MnII, or ZnII, in order to establish the priority among the ancillary metal ions in cooperating with the ferric heme and promoting its catalytic activity in oxidation reactions. pH-spectrophotometric titrations show that the presence of the non-heme metal decreases the pKa of water-bound to hemin (pKa = 8.4 ± 0.1), with a larger effect with iron(III), copper(II) and zinc(II) complexes (pKa of 6.4 ± 0.1, 6.0 ± 0.1 and 6.5 ± 0.1, respectively), which suggests that an interaction with the non-heme metal center takes place also at a micromolar range. NMR spectra indicate that the interaction between hemin and the non-heme center is not strong enough to convert the high spin configuration of FeIII–heme to low spin as observed for CcO and NOR enzymes. The dinuclear complex enhances the peroxidase-like activity of heme in kinetic studies performed at pH 5.5, 7.0 (using 3-(4-hydroxyphenyl)-propanoic acid as the substrate) and 9.0 (using o-phenylenediamine). In particular, the stronger effects are observed with FeIII, CuII, and CoII complexes, which increase the turnover rates of hemin throughout the pH range analyzed. At neutral and basic pH the KM value decreases up to one fourth indicating a positive cooperation between HMGH and [M(BBH)]n+ in binding the substrates. Moreover, the presence of the non-heme center facilitates the binding of H2O2 and formation of high valent ˙PFeIVO species. These data show that interaction between the two metal centers occurs with heme in several oxidation states.
    New Journal of Chemistry 01/2014; 38(2). · 3.16 Impact Factor
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    ABSTRACT: Dopaminergic neurons of the substantia nigra selectively degenerate over the course of Parkinson's disease. These neurons are also the most heavily pigmented cells of the brain, accumulating the dark pigment neuromelanin over a lifetime. The massive presence of neuromelanin in these brain areas has long been suspected as a key factor involved in the selective vulnerability of neurons. The high concentration of neuromelanin in substantia nigra neurons seems to be linked to the presence of considerable amounts of cytosolic dopamine that have not been sequestered into synaptic vesicles. Over the past few years, studies have uncovered a dual nature of neuromelanin. Intraneuronal neuromelanin can be a protective factor, shielding the cells from toxic effects of redox active metals, toxins, and excess of cytosolic catecholamines. In contrast, neuromelanin released by dying neurons can contribute to the activation of neuroglia triggering the neuroinflammation that characterizes Parkinson's disease. This article reviews recent studies on the molecular aspects of neuromelanin of the human substantia nigra.
    Neurotoxicity Research 10/2013; · 2.87 Impact Factor
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    ABSTRACT: The physiological functions of neuroglobin (Ngb), the heme protein of the globin family expressed in the nervous tissue, have not yet been clarified. Besides O2 storage and homoeostasis, Ngb is thought to play a role in neuroprotection as a scavenger of toxic reactive species generated in vivo under conditions of oxidative stress. Herein, the interaction of Ngb with the quinones generated by oxidation of catecholamines (dopamine, norepinephrine) and catechol estrogens (2-hydroxyestradiol, 4-hydroxyestradiol) and implicated in neurodegenerative pathologies like Parkinson's and Alzheimer's diseases, has been investigated. The cytotoxicity of quinones has been ascribed to the derivatization of amino acid residues (mainly cysteine) in proteins through the formation of covalent bonds with the aromatic rings. Combined studies of tandem mass spectrometry and protein unfolding indicate the presence of quinone-promoted modifications in all the Ngb derivatives analyzed (i.e. obtained employing either catecholamines or catechol estrogens as source of the reactive species). Among protein residues, the highest reactivity of cysteines (Cys46, Cys55, and Cys120 in human Ngb) towards quinone species has been confirmed and the dependence of the extent of protein modification on the method employed for catechol oxidation has been observed. When the oxidation reaction proceeds by one-electron steps, the involvement of semiquinone reactivity has been observed. The whole analysis of the data of Ngb modification suggests that the catecholamine oxidation products can extensively modify proteins (likely by catecholamine oligomers). The modification mediated by catechol estrogens is less pronounced but strongly affects the interactions with the solvent and the protein stability.
    Chemical Research in Toxicology 10/2013; · 3.67 Impact Factor
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    ABSTRACT: Hemoglobin (Hb) is the most abundant protein in human blood and we showed that under oxidative/nitrative stress conditions it is susceptible to cysteine oxidation, tyrosine nitration, and formation of a dimer of Hb subunits through tyrosine linkage. In the presence of hydrogen peroxide, Hb and its subunits efficiently convert nitrite into reactive nitrogen species, through reactions that are typical of peroxidases. If an exogenous phenolic substrate is present, Hb promotes its nitration with a fivefold higher efficiency with respect to the peroxidase-like phenol coupling reaction. In the absence of an exogenous substrate, the protein itself undergoes covalent modification. Trypsin treatment of Hb modified under conditions mimicking pathophysiological conditions, followed byHPLC-ESI-MS/MS analysis, allowed detection of nitration of Yα24, Yα42, Yβ130 and Yβ145, and conversion of Cα104, Cβ93 and Cβ112 into cysteine sulfinic acids. As additional biomarkers of nitrative stress, we found a covalent dimer of Hb αβ subunits and covalently linked heme-peptide. The dimer is selectively nitrated at Yα42. In a preliminary analysis of samples of human blood we found that low amounts of the dimer of subunits are always present. Therefore, if a correlation between the extent of Hb subunits coupling and pathological states could be established, this dimer could become an easily detectable biomarker of pathological conditions.
    Zeitschrift für anorganische Chemie 07/2013; 639(8‐9). · 1.16 Impact Factor
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    ABSTRACT: Stressful situation: Ferric heme binds to Aβ16 giving a mixture of five-coordinate [hemin(Aβ16)] and six-coordinate [hemin(Aβ16)2 ] species, the equilibrium of which depends on the Aβ16/hemin ratio and on temperature. Under oxidative and nitrative stress conditions the heme-Aβ16 complexes promote peroxidase-like reactions causing oxidation and nitration of the Aβ Tyr10 residue. Both dityrosine formation and tyrosine nitration strongly enhance Aβ aggregation.
    Angewandte Chemie International Edition 06/2013; · 11.34 Impact Factor
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    ABSTRACT: Mn(II)–Mn(II) cluster Apoenzyme Human prolidase, the enzyme responsible for the hydrolysis of the Xaa-Pro/Hyp peptide bonds, is a key player in the recycling of imino acids during the final stage of protein catabolism and extracellular matrix remodeling. Its metal active site composition corresponding to the maximal catalytic activity is still unknown, although prolidase function is of increasing interest due to the link with carcinogenesis and mutations in prolidase gene cause a severe connective tissue disorder. Here, using EPR and ICP-MS on human recombinant prolidase pro-duced in Escherichia coli (hRecProl), the Mn(II) ion organized in a dinuclear Mn(II)–Mn(II) center was identified as the protein cofactor. Furthermore, thermal denaturation, CD/fluorescence spectroscopy and limited proteoly-sis revealed that the Mn(II) is required for the proper protein folding and that a protein conformational modifi-cation is needed in the transition from apo-to Mn(II)loaded-enzyme. The collected data provided a better knowledge of the human holo-prolidase and, although limited to the recombinant enzyme, the exact identity and organization of the metal cofactor as well as the conformational change required for activity were proven.
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    Dataset: Hc-OPT
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    ABSTRACT: Contrary to earlier claims, the Cu(II) complex with the soluble Aβ16 peptide, and also that with Aβ28 exhibit no phenol monooxygenase (tyrosinase-like) activity; the complexes neither exhibit superoxide dismutase activity.
    Chemical Communications 04/2013; · 6.38 Impact Factor
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    ABSTRACT: The aggregation of α-synuclein (αS) is a critical step in the etiology of Parkinson's disease. Metal ions such as copper and iron have been shown to bind αS, enhancing its fibrillation rate in vitro. αS is also susceptible to copper-catalyzed oxidation that involves the reduction of Cu(II) to Cu(I) and the conversion of O(2) into reactive oxygen species. The mechanism of the reaction is highly selective and site-specific and involves interactions of the protein with both oxidation states of the copper ion. The reaction can induce oxidative modification of the protein, which generally leads to extensive protein oligomerization and precipitation. Cu(II) binding to αS has been extensively characterized, indicating the N terminus and His-50 as binding donor residues. In this study, we have investigated αS-Cu(I) interaction by means of NMR and circular dichroism analysis on the full-length protein (αS(1-140)) and on two, designed ad hoc, model peptides: αS(1-15) and αS(113-130). In order to identify and characterize the metal binding environment in full-length αS, in addition to Cu(I), we have also used Ag(I) as a probe for Cu(I) binding. Two distinct Cu(I)/Ag(I) binding domains with comparable affinities have been identified. The structural rearrangements induced by the metal ions and the metal coordination spheres of both sites have been extensively characterized.
    Inorganic Chemistry 01/2013; · 4.59 Impact Factor
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    ABSTRACT: Prolidase is the only human enzyme responsible for the digestion of iminodipeptides containing proline or hydroxyproline at their C-terminal end, being a key player in extracellular matrix remodeling. Prolidase deficiency (PD) is an intractable loss of function disease, characterized by mutations in the prolidase gene. The exact causes of activity impairment in mutant prolidase are still unknown. We generated three recombinant prolidase forms, hRecProl-231delY, hRecProl-E412K and hRecProl-G448R, reproducing three mutations identified in homozygous PD patients. The enzymes showed very low catalytic efficiency, thermal instability and changes in protein conformation. No variation of Mn(II) cofactor affinity was detected for hRecProl-E412K; a compromised ability to bind the cofactor was found in hRecProl-231delY and Mn(II) was totally absent in hRecProl-G448R. Furthermore, local structure perturbations for all three mutants were predicted by in silico analysis. Our biochemical investigation of the three causative alleles identified in perturbed folding/instability, and in consequent partial prolidase degradation, the main reasons for enzyme inactivity. Based on the above considerations we were able to rescue part of the prolidase activity in patients' fibroblasts through the induction of Heath Shock Proteins expression, hinting at new promising avenues for PD treatment.
    PLoS ONE 01/2013; 8(3):e58792. · 3.53 Impact Factor
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    ABSTRACT: Elucidating the structure and biosynthesis of neuromelanin (NM) would be an important step towards understanding its putative role in the pathogenesis of Parkinson's disease. A useful complement to studies aimed at unraveling the origin and properties of this essentially insoluble natural substance is the preparation of synthetic derivatives that resemble NM. With this aim in mind, water-soluble conjugates between dopamine-derived melanin and bovine serum albumin (BSA) were synthesized. Melanin-BSA adducts were prepared with both eumelanic oligomers obtained through the oxidative polymerization of dopamine and pheomelanic oligomers obtained under the same conditions from dopamine and cysteine. Iron ions were added during the synthesis to understand the interaction between the pigment and this metal ion, as the NM in neurons in several human brain regions contains significant amounts of iron. The structures of the conjugates were analyzed by (1)H NMR spectroscopy and controlled proteolysis/MS experiments. The binding of iron(III) ions was evaluated by ICP analysis and EPR spectroscopy. The EPR signal from bound iron(III) indicated high-spin octahedral sites and, as also seen for NM, the signal is coupled to a signal from a radical associated with the melanic components of the conjugates. However, the intensity of the EPR signal from iron suggested a reduced fraction of the total iron, indicating that most of the iron is strongly coupled in clusters within the matrix. The amount of paramagnetic, mononuclear iron(III) was greater in the pheomelanin-BSA conjugates, suggesting that iron clustering is reduced in the sulfur-containing pigment. Thus, the melanin-BSA conjugates appear to be good models for the natural pigment.
    European Journal of Biochemistry 10/2012; · 3.42 Impact Factor
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    ABSTRACT: Neuromelanins (NMs) are neuronal pigments of melanic-lipidic type which accumulate during aging. They are involved in protective and degenerative mechanisms depending on the cellular context, however their structures are still poorly understood. NMs from nine human brain areas were analyzed in detail. Elemental analysis led to identification of three types of NM, while infrared spectroscopy showed that NMs from neurons of substantia nigra and locus coeruleus, which selectively degenerate in Parkinson's disease, have similar structure but different from NMs from brain regions not targeted by the disease. Synthetic melanins containing Fe and bovine serum albumin were prepared to model the natural product and help clarifying the structure of NMs. Extensive nuclear magnetic resonance spectroscopy studies showed the presence of dolichols both in the soluble and insoluble parts of NM. Diffusion measurements demonstrated that the dimethyl sulfoxide soluble components consist of oligomeric precursors with MWs in the range 1.4-52 kDa, while the insoluble part contains polymers of larger size but with a similar composition. These data suggest that the selective vulnerability of neurons of substantia nigra and locus coeruleus in Parkinson's disease might depend on the structure of the pigment. Moreover, they allow to propose a pathway for NM biosynthesis in human brain.
    PLoS ONE 01/2012; 7(11):e48490. · 3.53 Impact Factor
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    ABSTRACT: Prolidase is a metallo-exopeptidase hydrolyzing X-Pro and X-Hyp dipeptides. Its absence or reduced level is typical in prolidase deficiency (PD) patients, and altered prolidase activity was reported in various diseases. Therefore, standardized and accurate measurement of prolidase activity is essential for PD diagnosis, as well as to elucidate the pathophysiology of other disorders. Human recombinant prolidase was used to optimize a spectrophotometric enzyme activity assay. Kinetic parameters and Mn(2+) affinity were evaluated. The method was validated on blood and fibroblasts from PD patients. An activation step consisting in prolidase incubation with 1 mmol/l MnCl(2) and 0.75 mmol/l reduced glutathione at 50°C for 20 min was necessary to obtain the maximum activity and to accurately determine, for the recombinant enzyme, V(max) (489 U/mg), K(m) (5.4 mM) and Mn(2+) affinity (54 mM(-1)). The method applied to PD diagnosis revealed an intra-assay CV=8% for blood and 9% for fibroblasts lysates. The inter-assay CV was 21% for blood and 20% for cell lysates. We optimized a faster spectrophotometric method to measure the activity when the enzyme is fully activated, this is crucial to allow a reliable evaluation of prolidase activity from different sources.
    Clinica chimica acta; international journal of clinical chemistry 06/2011; 412(19-20):1814-20. · 2.54 Impact Factor
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    ABSTRACT: The new poly-imidazole N(8) ligand (S)-2-piperazinemethanamine-1,4-bis[2-((N-(1-acetoxy-3-(1-methyl-1H-imidazol-4-yl))-2-(S)-propyl)-(N-(1-methyl-1H-imidazol-2-ylmethyl)))ethyl]-N-(phenylmethyl)-N-(acetoxy), also named (S)-Pz-(C2-(HisIm))(2) (L), containing three chiral (S) centers, was obtained by a multi-step synthesis and used to prepare dinuclear [Cu(2)(L)](4+) and trinuclear [Cu(3)(L)](6+) copper(II) complexes. Low-temperature EPR experiments performed on [Cu(2)(L)](4+) demonstrated that the two S = ½ centers behaved as independent paramagnetic units, while the EPR spectra used to study the trinuclear copper complex, [Cu(3)(L)](6+), were consistent with a weakly coupled three-spin ½ system. Theoretical models for the two complexes were obtained by DFT/RI-BP86/TZVP geometry optimization, where the structural and electronic characteristics nicely supported the EPR experimental findings. In addition, the theoretical analysis unveiled that the conformational flexibility encoded in both [Cu(2)(L)](4+) and [Cu(3)(L)](6+) arises not only from the presence of several σ-bonds and the bulky residues attached to the (S)-Pz-(C2-(HisIm))(2) ligand scaffold, but also from the poor coordination ability of the tertiary amino groups located in the ligand side-chains containing the imidazole units towards the copper(II) ions. Both the dinuclear and trinuclear complexes are efficient catalysts in the stereoselective oxidation of several catechols and flavonoid compounds, yielding the corresponding quinones. The structural features of the substrate-catalyst adduct intermediates were assessed by searching the conformational space of the molecule through MMFF94/Monte Carlo (MMFF94/MC) methods. The conformational flexibility of the bound ligand in the complexes proves to be beneficial for substrate binding and recognition. For the dinuclear complex, chiral recognition of the optically active substrates derives from weak electrostatic interactions between bound substrates and folded regions of the ligand scaffold. For the trinuclear complex, in the case of L/D-Dopa, the chiral recognition has a remarkable stereoselectivity index of 75%, the highest so far reported for this type of reaction. Here the dominant contribution to stereoselectivity arises from the direct interaction between a donor group (the Dopa carboxylate) far from the substrate reaction site (the catechol ring) with the additional (third) copper center not involved in the oxidative catalysis. On the other hand, in the case of bulky substrates, such as L/D-catechin, the observed poor substrate recognition is associated with much weaker interactions between the chiral regions of the complex and the chiral part of the substrate.
    Dalton Transactions 02/2011; 40(20):5436-57. · 4.10 Impact Factor
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    ABSTRACT: The combination of terepthaloylbisglycinate (TBG2−) and metal ions at room temperature results in the formation of five coordination polymers formulated as [M(μ-TBG)(μ-H2O)(H2O)2]·2H2O, where M = Co (1) and Cu (2), [Mn(μ-TBG)(H2O)4]·2H2O (3), [Cd(μ-TBG)(H2O)3]·2H2O (4) and [Pb(μ-TBG)(H2O)2]·3H2O (5). The dimensionality of the final product is affected by the coordination number of the metal ion. Thermal, reversible solvent uptake, magnetic and catalytic properties of these compounds have been investigated.
    New Journal of Chemistry 01/2011; 35:1060. · 3.16 Impact Factor
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    ABSTRACT: A mild copper-mediated halogenation reaction of phenolic rings is reported. The reaction of bis(2-hydroxybenzyl)-1,3-diaminopropane (H2bhbd) with copper(II) chloride in acetonitrile generates linear trinuclear [Cu3(bhcbd)2Cl2](CH3CN), containing modified ligands, whose phenol moieties are selectively chlorinated at the 5-position. Under comparable experimental conditions with copper(II) bromide, bromination of the ligand is observed, albeit at a slower reaction rate. In the presence of trialkylorthoformates, which are used as dehydrating agents, a ring closure of the ligand is observed after removal of copper to yield a product with a six-membered ring. This product has been isolated and characterized by NMR spectroscopy and MS. Similarly, bromination of bis(2-hydroxybenzyl)-1,3-diiminopropane (H2bhbdi) occurs in the presence of copper(II) bromide, with concomitant formation of a linear trinuclear complex. Surprisingly, an asymmetric dinuclear copper(II) coordination compound without chlorination of the ligand is obtained when the related ligand bis(2-hydroxybenzyl)-1,3-diminopropane (H2bhbdi) reacts with copper(II) chloride.
    European Journal of Inorganic Chemistry 01/2011; · 3.12 Impact Factor
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    Chemistry Letters 01/2011; 40:1360. · 1.59 Impact Factor

Publication Stats

1k Citations
652.69 Total Impact Points


  • 1992–2014
    • University of Pavia
      • • Department of Chemistry
      • • Department of Molecular Medicine
      Ticinum, Lombardy, Italy
  • 2010
    • Sapienza University of Rome
      • Department of Chemistry
      Roma, Latium, Italy
  • 1998–2010
    • University of Padova
      • Department of Biology
      Padova, Veneto, Italy
  • 2008
    • Università degli Studi di Siena
      • Department of Life Sciences
      Siena, Tuscany, Italy
  • 1983–2008
    • University of Milan
      • • Department of Inorganic, Organometallic and Analytical Chemistry "Lamberto Malatesta" CIMA
      • • Department of Organic and Industrial Chemistry
      Milano, Lombardy, Italy
  • 2004
    • University of Valencia
      • Departamento de Química Inorgánica
      Burjassot, Valencia, Spain
    • Università degli Studi di Genova
      Genova, Liguria, Italy
  • 2003
    • University of Florence
      • CERM - Centro di Ricerca di Risonanze Magnetiche
      Florence, Tuscany, Italy