The dissolution of monosodium urate monohydrate crystals: formulation of a biocompatible buffer solution with potential use in the treatment of gouty arthropathies

The dissolving abilities (DAs) of several aqueous media for microcrystalline monosodium urate monohydrate (MSU, NaC5N4O3H3·H2O) have been investigated using UV spectrophotometry for quantitative analytical determinations and X-ray diffraction, scanning electron microscopy and polarized light optical microscopy to assess structural aspects. High DAs were found for a buffer labeled TMT which contains tris(hydroxymethyl)aminomethane (TRIS), tris(hydroxymethyl)aminomethane hydrochloride (TRIS·HCl), D-mannitol (MAN) and taurine (TAU) and gave DA30=1298(5) mg/L for synthetic MSU after 30 min incubation at 37°C and pH 7.4, most of the dissolution taking place within the first 5-10 min. Semiempirical molecular modelling techniques (ZINDO/1) show a favorable energy balance for the formation of a TRIS-urate-TRIS adduct which might explain the high DA values. Buffers containing linear or dendrimeric polyamines gave DA values which suggest that complex formation toward sodium cations is less important. An ex vivo MSU sample was found to have a significantly lower DA value (DA30=1124(5) mg/L in TMT) as well as a lower crystallinity than its synthetic counterpart, possibly related to the presence of a non-crystalline impurity such as endogenous proteins. Cytotoxicity tests based on the MTT assay were used to check the biocompatibility of the TMT buffer and showed only moderate cell mortality after 24 h contact with the buffer solution

Effect of Free Water Molecules on the Structure of Mg-ATP-Dipyridylamine and Overview on Selected Metal-Adenosine Triphosphate Structures in Model Compounds and in Enzymes

The X-ray diffraction (XRD) structures for new isoforms of [M(H2O)6]·[M(HATP)2]·2(HDPA)·xH2O, ATP = adenosine 5’-triphosphate, DPA = 2,2’-dipyridylamine, M = Mg(II), x = 6H2O, 1, M = Ca(II), x = 8H2O, 2 were determined by using rotating anode on molybdenum target X-ray source and Kappa CCD with confocal focusing mirror. The accuracy of the presently refined structure for 1 is the highest reported so far based on agreement factors (R1 = 0.0579) and estimated standard deviations (esds) on geometrical parameters. The comparative analysis was extended to the structures of other low molecular weight metal-triphosphate complexes, to the structures of metal-triphosphate-protein systems as well as to computed models of metal-triphosphate complexes. The structures of 1 and 2 reported in this work show that on changing the number of co-crystallized water molecules, the interaction of the metal to the phosphate chain (for 1) and the conformation of ribose (for 2) undergo subtle but significant changes. Interestingly, the vast majority of Mg-nucleoside triphosphate (NTP)-enzyme systems have similar pattern of coordination to the phosphate chain when compared to 1 and 2. The three phosphate groups have variable M-O bond distances, depending on the systems. The structures for 1 and 2 have a high significance as general model compounds for experimental solid state and computations for these types of biological systems

Oxygen Radical Scavenger Activity, EPR, NMR, Molecular Mechanics and Extended-Hückel Molecular Orbital Investigation of the Bis(Piroxicam)Copper(II) Complex

The oxygen radical scavenger activity (ORSA) of [CuII(Pir)2] (HPir = Piroxicam = 4-hydroxy -2- methyl -N-2- pyridyl -2H- 1,2-benzothiazine -3- carboxamide 1,1-dioxide) was determined by chemiluminescence of samples obtained by mixing human neutrophils (from healthy subjects) and [CuII(Pir)2(DMF)2] (DMF = N,N -dimethylformammide) in DMSO/GLY/PBS (2:1:2, v/v) solution (DMSO = dimethylsulfoxide, GLY = 1,2,3-propantriol, PBS = Dulbecco’s buffer salt solution). The ratio of the residual radicals, for the HPir (1.02·10−4M) and [CuII(Pir)2(DMF)2] (1.08·10−5M)/HPir (8.01·10−−5M) systems was higher than 12 (not stimulated) [excess of piroxicam was added (Cu/Pir molar ratio ≈1:10) in order to have most of the metal complexed as bischelate]. In contrast, the ratio of residual radicals for the CuCl2 (1.00·10−5M) and [CuII(Pir)2(DMF)2] (1.08·10−5M)/Hpir (8.01·10−5M)system was 5. The [CuII(Pir)2] compound is therefore a stronger radical scavenger than either HPir or CuCl2. A molecular mechanics (MM) analysis of the gas phase structures of neutral HPir, its zwitterionic (HPir+-) and anionic (Pir-) forms, and some CuII-piroxicam complexes based on X-ray structures allowed calculation of force constants. The most stable structure for HPir has a ZZZ conformation similar to that found in the CuII (and CdII complexes) in the solid state as well as in the gas phase. The structure is stabilized by a strong H bond which involves the N(amide)-H and O(enolic) groups. The MM simulation for the [CuII(Pir)2(DMF)2] complex showed that two high repulsive intramolecular contacts exist between a pyridyl hydrogen atom of one Pir- molecule with the O donor of the other ligand. These interactions activate a transition toward a pseudo-tetrahedral geometry, in the case the apical ligands are removed. On refluxing a suspension of [CuII(Pir)2(DMF)2] in acetone a brown microcystalline solid with the Cu(Pir)2·0.5DMF stoichiometry was in fact prepared. 13C spin-lattice relaxation rates of neutral, zwitterionic and anionic piroxicam, in DMSO solution are explained by the thermal equilibrium between the three most stable structures of the three forms, thus confirming the high quality of the force field. The EPR spectrum of [CuII(Pir)2(DMF)2] (DMSO/GLY, 2:1, v/v, 298 and 110 K) agrees with a N2O2+O2 pseudo-octahedral coordination geometry. The EPR spectrum of [CuII(Pir)2·0.5DMF agrees with a pseudo-tetrahedral coordination geometry. The parameters extracted from the room temperature spectra of the solution phases are in agreement with the data reported for powder and frozen solutions. The extended-Hückel calculations on minimum energy structures of [CuII(Pir)2(DMF)2] and [CuII(Pir)2] (square planar) revealed that the HOMOs have a relevant character of dx2−y2. On the other hand the HOMO of a computer generated structure for [CuII(Pir)2] (pseudo-tetrahedral) has a relevant character of dxy atomic orbital. A dxy orbital is better suited to allow a dπ-pπ interaction to the O2- anion. Therefore this work shows that the anti-inflammatory activity of piroxicam could be due in part to the formation of [CuII(Pir)2] chelates, which can exert a SOD-like activity

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

[CdII(μ2-O2,Oâ\u80², Oâ\u80³-SO4)(terpy)]2·2H2O, 1·2H2O (terpy, 2,2â\u80²:6â\u80²,2â\u80³-terpyridine) was obtained from the reaction of 3 CdSO4·8H2O 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,Oâ\u80²-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/(6-31 G**, S) levels. The computations reproduced well the main features of the Zn(μ2-O,Oâ\u80²-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

Heavy metals in drinking waters from Mount Amiata (Tuscany,Italy). Possible risks from arsenic for public health in the Provinceof Siena

Concentrations of As, Al and some heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb) were measured in drinking waters from Siena and Grosseto districts, South Tuscany, Italy. The analysis, performed mostly by electrothermal activated atomic absorption spectroscopy equipped with graphite furnace, and in some cases highresolution inductively coupled plasma mass spectrometry, indicated that concentrations of the elements were generally far below the maximum allowed concentration (MAC). However, the concentration of As in some of the waters at sources or at the terminals of the water webs was relatively high (largest value, 14.4(2) mgyl) when compared to the MAC value (As 10 mgyl, December 25, 2003; Italian Law). Relatively high concentrations of some metals had been detected in a few samples from the ends of the distribution webs, when compared to values at sources. These effects are probably due to leaching from metal pipes. A general ‘metal index’ (MI) for drinking water, which takes into account possible additive effects of N heavy metals on the human health that helps to quickly evaluate the overall quality of drinking waters, is introduced in this paper as MIs8is1,NwCiy(MAC)ix. Samples from Ermicciolo spring and Siena water web had MI values of 1.1 and 1.3, respectively, showing that the quality of drinking water in town is somewhat worse than that at one of the main sources, at least regarding the 12 elements taken into account. 2003 Elsevier B.V. All rights reserved