Gabriella Tamasi

fac-{Ru(CO)3}2+ Selectively Targets the Histidine Residues of the β-Amyloid Peptide 1-28. Implications for New Alzheimer's Disease Treatments Based on Ruthenium Complexes

The reaction of the ruthenium(II) complex fac-[Ru(CO)(3)Cl(2)(N(1)-thz)] (I hereafter; thz = 1,3-thiazole) with human beta-amyloid peptide 1-28 (Abeta(28)) and the resulting {Ru(CO)(3)}(2+) peptide adduct was investigated by a variety of biophysical methods. (1)H NMR titrations highlighted a selective interaction of {Ru(CO)(3)}(2+) with Abeta(28) histidine residues; circular dichroism revealed the occurrence of a substantial conformational rearrangement of Abeta(28); electrospray ionization mass spectrometry (ESI-MS) suggested a prevalent 1:1 metal/peptide stoichiometry and disclosed the nature of peptide-bound metallic fragments. Notably, very similar ESI-MS results were obtained when I was reacted with Abeta(42). The implications of the above findings for a possible use of ruthenium compounds in Alzheimers disease are discussed.

Synthesis, spectroscopic and DFT structural characterization of two novel ruthenium(III) oxicam complexes. In vivo evaluation of anti-inflammatory and gastric damaging activities

The reactions of ruthenium(III) chloride trihydrate with piroxicam (H2PIR) and tenoxicam (H2TEN), two widely used non-steroidal anti-inflammatory drugs, afforded [Ru(III)Cl2(H2PIR)(HPIR)],·1, and [Ru(III)Cl2(H2TEN)(HTEN)],·2. Both compounds were obtained as pure green solids through purification via flash column chromatography. Characterizations were accomplished through UV-vis and IR spectroscopy, potentiometry and HPLC. Quantum mechanics and density functional computational methods were applied to investigate their respective molecular structures. The experimental and computational results are in agreement with a pseudo-octahedral coordination where the two chlorido ligands are in trans positions (apical) and the two trans-N,O chelating oxicam ligands occupy the equatorial sites. Both compounds revealed an acceptable solubility and stability profile upon dissolution in a standard buffer at physiological pH. Nonetheless, the addition of biologically occurring reducing agents caused spectral changes. The two complexes manifested a poor reactivity with the model proteins cytochrome c and lysozyme: no evidence for adduct formation was indeed obtained based on a standard ESI MS analysis; in contrast, some significant reactivity with serum albumin was proved spectrophotometrically. Remarkably, both study compounds revealed pronounced anti-edema effects in vivo suggesting that the pharmacological actions of the ligands are mostly retained; in addition, they were less irritating than piroxicam on the gastric mucosa when the coordination compounds and free oxicam were administered at the same overall molar concentration of the ligand. Overall, the present results point out that ruthenium coordination may represent an effective strategy to improve the pharmacological properties of oxicam drugs reducing their undesired side effects.

{Ru(CO)x}-Core complexes with benzimidazole ligands: synthesis, X-ray structure and evaluation of anticancer activity in vivo

The reaction of [Ru(CO)6Cl2], 1, with N[combining low line]3-methylbenzimidazole (MBI) and 5,6-dimethylbenzimidazole (DMBI) afforded two new complexes with the general formula fac-[RuII(CO)3Cl2L], L = MBI (2) or DMBI (4). Crystals of cis,trans-[RuII(CO)2Cl2(N[combining low line]3-MBI)2], 3, were also obtained from the mother liquor that produced 2. In the presence of water, the dissociation of Ru-N, Ru-Cl and Ru-CO bonds occurred as a function of time, water content and pH. Density functional theory structure simulations/optimizations were carried out at the Becke3LYP level of theory for evaluating the relative stability of possible conformers. ESI-MS studies revealed the ability of the complexes to link model proteins, such as lysozyme, bovine pancreatic ribonuclease and cytochrome c, with the partial release of the heteroaromatic base, chlorido and carbonyl ligands. X-ray diffraction studies on crystals grown from a solution of HEWL and 2 showed the partial removal of chloride and CO. Cytotoxicity tests yielded two-digit micromolar IC50 values in CH1/PA-1 and SW480 cancer cells. In contrast to CORM-3 and 2, a significantly reduced tumor growth was observed with 4 in the murine colon cancer CT-26 model in vivo.

Copper(I)-alkyl sulfide and -cysteine tri-nuclear clusters as models for metallo proteins: a structural density functional analysis

After having set up the computational methodology for Cu(I)-sulfur systems as models for copper proteins, namely using the simple ligands H2S, HS−, CH3SH, and CH3S−, the Cu(I)-Cysteine systems have been investigated: [CuI( S -H2Cys) n ]+ (H2Cys, cysteine, NH2,SH,COOH) [CuI( S -HCys) n ]1− n (NH2,S−,COOH). Finally, the structures for bi-nuclear (Et, CH2CH3), and tri-nuclear [CuI( S -SH)]3, , , , (NH2,SH,COOH), (NH2,S−,COOH, and NH2,SH,COO−), as well as (NH2,S−,COO−), were also optimized to mimic the active center for a metallo-chaperone copper transport protein (CopZ). The X-ray structures for the biomolecules were matched fairly well as regards the Cu–S bond distances and Cu…Cu contact distances in the case the model cysteine S atom is deprotonated. Upon protonation of ligand S atoms, the conformation of clusters is altered and might bring about the di- and tri-nuclear core breakage. These findings suggest that subtle protonation/deprotonation steps, i.e. small and/or local pH changes play a significant role for copper transport processes.

Effect of resveratrol on platelet aggregation by fibrinogen protection

The effect of resveratrol (RSV) in inhibiting platelet adhesion and aggregation, as well as fibrinogen (FBG) conformational changes promoted by epinephrine (EP), were studied, by using complementary experimental techniques. NMR and IR spectroscopies were used to investigate possible protective effects by RSV towards FBG, in presence of EP. The protective effect of RSV towards FBG was highlighted by spin nuclear relaxation experiments that were interpreted for determining the thermodynamic equilibrium constants of FBG-EP interaction, and by infrared measurements, that showed EP-induced conformational changes of FBG. The ability of RSV in inhibiting platelet adhesion and aggregation promoted by EP was evaluated by scanning electron microscopy (SEM), measuring the platelet adhesion and aggregation degree, in comparison to data obtained for platelet aggregation in platelet rich plasma (PRP). The experimental combined approach pointed out that RSV is able to protect both FBG and platelets from the denaturant and aggregating action of EP at stress level concentration.

Simulating the active sites of copper-trafficking proteins. Density functional structural and spectroscopy studies on copper(I) complexes with thiols, carboxylato, amide and phenol ligands

Abstract A series of mononuclear binary and ternary Cu(I) complexes with formato, formamide, methylphenol, and methanethiolato ligands were optimized at DFT-B3LYP/6-31G** (BS1) and DFT-B3LYP/6-311++G** (BS2) levels of theory. The solvent effect was taken into account via PCM method (BS1W and BS2W, respectively). The coordination arrangement for [CuI(SCH3/S(H)CH3)(OOCH)]−/0 and [CuI(SCH3/S(H)CH3)(O(H)(C6H4)CH3)]0/+ was pseudo-linear and for [CuI(SCH3/S(H)CH3)(OOCH)(OC(H)NH2)]−/0 was pseudo-trigonal. The [CuI(S-S(H)CH3/CuI(S-SCH3)]+/0 link even to amide carbonyl and to general O(H)R residues (R=C6H5CH3). [CuI(SCH3)2(O(H)(C6H4)CH3)]− went towards dissociation of the O(H)(C6H4)CH3 ligand, whereas [CuI(S(H)CH3)2(O(H)(C6H4)CH3)]+ converged nicely, maintaining the hydroxy function linked to the metal. The trends of total electronic energies seemed to be significant, suggesting that linear CuIS2 coordination is more suitable than CuIS, CuIS3 and CuIS4 arrangements. The formation energies of [CuI(S(H)CH3/SCH3)(OOCH)]0/−1 were higher than those of [CuI(S(H)CH3/SCH3)2]+/− on starting from [CuI(S(H)CH3/CuI(SCH3)]+/0 by ca. 11–9 kcal mol−1 (BS2W). The structural arrangements, bond distances, and angles as well as computed spectroscopic parameters resulted in good agreement with experimental data for corresponding synthetic complexes and with metal site regions of several copper(I)-proteins. These data help in interpreting structural data of complex biological systems and in constructing reliable force fields for molecular mechanics computations.

X-ray structure and density functional theory studies of an unexpected product: trans-bis{2-[(2-cyanoethyl)iminomethyl]phenolato}copper(II).

The title compound, [Cu(C(10)H(9)N(2)O)(2)] or [Cu(II)(CYMB)(2)], (I), was obtained in an attempt to reduce trans-bis(2-{[3,5-bis(trifluoromethyl)phenyl]iminomethyl}phenolato)copper(II), [Cu(TIMB)(2)], (II), with bis(pentamethylcyclopentadienyl)cobalt(II) [decamethylcobaltocene, Cp*(2)Co, (III)]. The molecular structure of (I) has the Cu(II) centre located on an inversion centre of the C2/c space group. A density functional theory (DFT) analysis at the B3LYP/Lanl2dz(CuF);6-31G**(CHNO) level performed in order to optimize the structures of the free ligands CYMB(-) and TIMB(-), and the metal complexes [Cu(I/II)(CYMB)(2)](-/0) and [Cu(I/II)(TIMB)(2)](-/0), reproduced well the X-ray diffraction structure and allowed us to infer the insertion of the cyanomethide anion on the 3,5-bis(trifluoromethyl)phenyl system from an evaluation of the Mulliken atomic charges and the electronic energies.

[RuII(NO+)]3+-core complexes with 4-methyl-pyrimidine and ethyl-isonicotinate: synthesis, X-ray structure, spectroscopy, and computational and NO-release studies upon UVA irradiation.

The reaction of RuCl(3)(NO).H(2)O with 4-methylpyrimidine (MePYM) and ethylisonicotinate (EINT), in absolute ethanol at 40-55 degrees C afforded crystalline trans-[RuCl(3)(NO)L(2)] complexes. Structural studies via X-ray diffraction, and spectroscopic methods (NMR, IR, UV-visible (UV-Vis)) revealed that the molecular structures have the two Ls in trans positions (axial) and the chloride anions and the NO(+) cation as equatorial ligands; pyrimidine...pyrimidine pairing pattern via two weak C-H...N interactions occur. The molecular structures for the EINT derivative was inferred from spectroscopy and computations. Under irradiation at 366 nm several solutions of the title compounds deliver NO via first order processes. Visible light (420-700 nm) does not produce significant NO release from CH(2)Cl(2) and CH(3)CN solutions within 24h.

Study of binary and ternary metal complexes containing the sulfato ligand: molecular models for selected non-catalytic sites in sulfurylase

[CdII(μ2-O2,O′,O″-SO4)(terpy)]2·2H2O, 1·2H2O (terpy, 2,2′:6′,2″-terpyridine) was obtained from the reaction of 3CdSO4·8H2O with terpy and consists of centrosymmetric dimeric units in which the two Cd(terpy)2+ moieties are held together by two tridentate sulfato anions that act as chelators towards the two metal centres, one oxygen being tri-coordinate. This coordination mode for the sulfato ligand has never been reported before in the solid state. [ZnII(μ2-O,O′-SO4)(terpy)]2·2H2O, 2·2H2O, was obtained by using ZnSO4·7H2O through a procedure similar to that followed for 1·2H2O. Semi-empirical quantum mechanics and density functional structure optimisations were performed at the AM1 and Becke3LYP/(6-31G**, S) levels. The computations reproduced well the main features of the Zn(μ2-O,O′-SO4)2Zn unit as found in 2. A [Zn(imidazole)2(O-OOCCH3)2(O-SO4)]2− model was also optimised as a model for ATP-sulfurylase from Saccharomices cerevisae.

Grappa quality from the Chianti and Montepulciano areas (Tuscany, Italy): Monitoring the leaching of copper from distillation columns

The main aim of this work was to evaluate the leaching of copper in grappa from distillation plant that treats Cabernet and Sangiovese marcs (Montepulciano and Chianti, Tuscany). Copper content (determined by atomic absorption spectrometry, AAS) was 1.05 0.03 mg L 1 in industrial distillates (Cabernet marc, 82.3% alcohol, v/v), and 3.7 0.2 lg L 1 in artificial grappa (62.0%, Cabernet) obtained by distilling marc in a laboratory-scale glassware plant. The artificial grappa distillate was refluxed over copper shavings, and copper content, CCu, was analysed in relation to reflux time and wear of the copper bell. The results showed that CCu trend was almost linear with increasing alcohol concentration and constant reflux time, and vice versa. The ratios of selected volatile components were not influenced by reflux on the shavings.