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PubMed2000

The nickel-substituted quasi-Wells-Dawson-type polyfluoroxometalate,

A series of transition metal substituted polyfluorooxometalates (PFOM) [M(L)H2F6NaW17)55]q-, M= Zn2+ , Co2+, Mn2+, Fc2+, Ru2+, Ni2+ and V5+ and L=H2O, O2-, of quasi-Wells-Dawson structure, was synthesized. In the series prepared, only the nickel-substituted polyfluorooxometalate was capable of catalytic activation of hydrogen peroxide in biphasic reaction media, the reaction leading mainly to the selective epoxidation of alkenes and alkenols. The manganese-, cobalt-, ruthenium-, iron-, vanadium-, and zinc-substituted polyfluorooxometalates were catalytically inactive, although, except for the zinc polyfluorooxometalate, very significant catalase activity was observed. Oxidation of thianthrene showed that sulfoxides were oxidized more easily than sulfides. Kinetic profiles of cyclooctene epoxidation showed that the reaction was zero order in both cyclooctene and hydrogen peroxide. Hydrogen peroxide was consumed at a rate 40% higher than the rate of epoxidation of cyclooctene. The reaction appears to proceed through an intermediate peroxo/hydroperoxo species that was observed in the IR spectrum. Atomic absorption, IR and 19F NMR spectroscopy indicated that the [Ni(H2O)H2F6NaW17O55]9- compound was stable under reaction conditions.

Journal Article↗

PubMed1969

Metal complexes of mycobactin P and of desferrisideramines.

Crystalline gallium mycobactin P and chromic mycobactin P have been prepared. The chromic compound, unlike other metallic complexes of mycobactin P, does not detectably exchange its metal with ferric iron; it competitively antagonizes the growth-promoting action of mycobactin P towards Mycobacterium johnei. Mycobactin P, desferrioxamine B and desferrichrysin form coloured 1:1 complexes with ammonium vanadate. The vanadyl complexes of the water-soluble desferrisideramines are formed in aqueous solution. Two distinct forms occur at pH7 and pH3; these are slowly interconvertible when the pH is changed. The complexes show other changes at lower pH values; unlike other metallic desferrisideramine complexes, the vanadyl compounds do not dissociate even in the strongest acids, but dissociate above pH9. Their properties have been studied spectrophotometrically, by electrophoresis and by electrometric titration. The affinity of mycobactin for ferric iron is greater than that of desferrioxamine B under two different conditions of measurement.

Chromium↗

PubMed2001

Structural characterization and magnetic properties of sandwich-type tungstoarsenate complexes. Study of a mixed-valent VIV2/VV heteropolyanion.

Complexes K11Na1[As2W18(Mn(H2O))3O66]x27H2O (1) and Na12[As2W18(Co(H2O))3O66]x34H2O (2) have been characterized. 1 crystallizes in the orthorhombic space group Pnma, with a = 30.6484(4) A, b = 14.9946(2) A, and c = 19.17080(10) A (Z = 4), while 2 crystallizes in the monoclinic space group C2/c, with a = 14.124(2) A, b = 23.294(3) A, c = 32.247(3) A, and beta = 98.935(10) degrees (Z = 4). Structures of the anions of 1 and 2 are similar, the divalent metals adopting a square pyramidal environment. K11[As2W18(VO)3O66]x23H2O (3) crystallizes in the orthorhombic space group Pnma, with a = 30.6240(5) A, b = 14.9861(2) A, and c = 19.2651(3) A (Z = 4). The structure has revealed a disorder on two of the three metals linking the [alpha-AsW9O33]9- parts. For these two vanadium atoms, the V=O bonds are directed alternatively toward the inside or the outside of the [alpha-AsW9O33]9- cavity. The remaining vanadium shows a V=O bond always directed toward the outside of the cavity. Titration of VIV by CeIV revealed that 3 is the mixed-valent VIV2VV species. Magnetic measurements are in agreement with this formulation. The high-temperature molar magnetic susceptibility of a powdered sample of 3 clearly confirms the presence of two d1 centers. The two VIV are antiferromagnetically coupled, with J = -2.9 cm-1 and g = 1.93. Crystallographic data do not permit the location of the two VIV to be distinguished from the location of the VV. As expected, the Mn(II) are very weakly antiferromagnetically coupled in compound 1. The complex Na8[Ni(H2O)6]2[As2W18(Ni(H2O))3O66]x20H2O (4) has been synthesized. The anion crystallized with two octahedral [Ni(H2O)6]2+ as counterions. Magnetic data have been fitted assuming that the only exchange-coupled centers are the nickels of the polyanion. 4 exhibits an antiferromagnetic coupling with J = -1.7 cm-1, g = 2.27, and theta = -1.5 K.

Journal Article↗

PubMed1999

A physicochemical study of the tetracycline coordination to oxovanadium(IV).

The interaction of tetracycline and oxovanadium(IV) in aqueous solution was studied by potentiometric and spectrophotometric methods. Oxovanadium(IV) ions form both a positively charged 1:1 and a neutral 2:1 metal-ligand complex with tetracycline. When a 1:1 ligand-to-metal ratio mixture is used at about pH 4.5 the 1:1 species predominates, being replaced at pH 6 by the binuclear complex. The binuclear complex has been isolated and fully characterised. Infrared and EPR studies suggest the existence of two distinct vanadyl binding sites. Our results indicate that the first vanadium coordinates to the BCD-ring system and the second one to the A-ring. Biological implications of the existence of a neutral complex at physiological pH are briefly discussed.

Anti-Bacterial Agents↗

PubMed1995

Oxidative mechanisms in the toxicity of metal ions.

The role of reactive oxygen species, with the subsequent oxidative deterioration of biological macromolecules in the toxicities associated with transition metal ions, is reviewed. Recent studies have shown that metals, including iron, copper, chromium, and vanadium undergo redox cycling, while cadmium, mercury, and nickel, as well as lead, deplete glutathione and protein-bound sulfhydryl groups, resulting in the production of reactive oxygen species as superoxide ion, hydrogen peroxide, and hydroxyl radical. As a consequence, enhanced lipid peroxidation. DNA damage, and altered calcium and sulfhydryl homeostasis occur. Fenton-like reactions may be commonly associated with most membranous fractions including mitochondria, microsomes, and peroxisomes. Phagocytic cells may be another important source of reactive oxygen species in response to metal ions. Furthermore, various studies have suggested that the ability to generate reactive oxygen species by redox cycling quinones and related compounds may require metal ions. Recent studies have suggested that metal ions may enhance the production of tumor necrosis factor alpha (TNF alpha) and activate protein kinase C, as well as induce the production of stress proteins. Thus, some mechanisms associated with the toxicities of metal ions are very similar to the effects produced by many organic xenobiotics. Specific differences in the toxicities of metal ions may be related to differences in solubilities, absorbability, transport, chemical reactivity, and the complexes that are formed within the body. This review summarizes current studies that have been conducted with transition metal ions as well as lead, regarding the production of reactive oxygen species and oxidative tissue damage.

Animals↗

PubMed2006

High-valent transition metal corrolazines.

High-valent metalloporphyrin intermediates have been implicated as key players in numerous mechanistic proposals for both biological (e.g., heme protein) and synthetic porphyrin mediated transformations. However, the direct observation of these species is quite challenging because of the inherently short lifetimes of many of these metalloporphyrin intermediates. This review focuses on our own efforts to synthesize and study a new class of porphyrinoid compounds called corrolazines, which are designed to stabilize high-valent species for direct analysis. These compounds are related to corroles, which also exhibit the unusual ability to stabilize high oxidation states, and the reactivity and physical properties of relevant corrole and porphyrin analogs are compared with the appropriate corrolazines. The chemistry of Cu, Co, V, and Mn are highlighted, with a particular emphasis on the reactivity of high-valent manganese-oxo complexes.

Cobalt↗

PubMed2003

A novel series of materials composed of arrays of vanadium oxide container molecules, [V18O42(X)] (X = H2O, Cl-, Br-): synthesis and characterization of [M2(H2N(CH2)2NH2)5][(M(H2N(CH2)2NH2)2]2V18O42(X)]. 9H2O (M = Zn, Cd).

The synthesis and characterization of the novel systems [Zn(2)(H(2)N(CH(2))(2)NH(2))(5)][(Zn(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(H(2)O)].9H(2)O (1), [Cd(2)(H(2)N(CH(2))(2)NH(2))(5)][(Cd(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(Br)].9H(2)O (2), and [Zn(2)(H(2)N(CH(2))(2)NH(2))(5)][(Zn(H(2)N(CH(2))(2)NH(2))(2))(2)V(18)O(42)(Cl)].9H(2)O (3) have been described. These materials represent a new class of solids that have been prepared by combining conventional coordination compounds with spherical polyoxovanadate clusters. The isomorphous structures of these hybrid solids consist of two-dimensional arrays of container cluster molecules [V(18)O(42)(X)] (X = H(2)O, Br-, Cl-) interlinked by the transition metal complex moieties [M(H(2)N(CH(2))(2)NH(2))(2)] (M = Zn, Cd). These compounds contain an unprecedented complex cation, [M(2)(H(2)N(CH(2))(2)NH(2))(5)](4+). Crystal data for 1: C(9)H(46)N(9)O(26)V(9)Zn(2), monoclinic space group P2(1)/m (No. 11), a = 12.3723(7) A, b = 20.9837(11) A, c = 15.8379(8) A, beta = 97.3320(10) degrees, Z = 4.

Journal Article↗

PubMed1982

Stimulatory (insulin-mimetic) and inhibitory (ouabain-like) action of vanadate on potassium uptake and cellular sodium and potassium in heart cells in culture.

(1) The influence of vanadate (Na3VO4) on sodium and potassium uptake as well as on cellular ion contents of sodium and potassium has been studied in heart muscle and non-muscle cells obtained from various species. An ouabain-like inhibition of potassium uptake (up to 50%), combined with a decrease of cellular potassium (up to 20%) has been observed by vanadate (10(-4)-10(-3) M) in heart non-muscle cells obtained from neonatal guinea pigs and chick embryos. In heart muscle and non-muscle cells prepared from neonatal rats, as well as in Girardi human heart cells, a vanadate-induced stimulation of potassium uptake (up to 100%), combined with a rise in cellular potassium (up to 20%) and without significant alteration of cellular sodium, has been found. A slight increase of 22Na+ influx can be measured in rat heart muscle cells and in Girardi human heart cells in the presence of vanadate (10(-4)--10(-3) M). (2) In beating rat heart muscle cells in culture, detrimental effects of serum deprivation--concerning beating properties, potassium uptake and cellular potassium--can at least in part be overcome by addition of vanadate. Furthermore, this compound prevents ouabain-induced signs of toxicity (contractures) in these cells. (3) The stimulatory effects of vanadate on potassium can be mimicked by insulin (1-10 mU/ml). Furthermore, vanadate produces an insulin-like stimulation of 2-deoxy-D-glucose uptake in rat heart muscle and non-muscle cells as well as in Girardi human heart cells. (4) The experimental data demonstrate an ouabain-like inhibition as well as an insulin-mimetic stimulation of potassium-uptake in various heart cells. The reason for this antagonistic mode of action may be due to the different capabilities of the heart cell types to reduce vanadium in the V-valence state of vanadium in the IV-valence state, thereby favouring either ouabain-like inhibition (vanadium V) or insulin-mimetic stimulation (vanadium IV) of potassium transport.

Animals↗

PubMed1982

The comparison of vanadyl (IV) and insulin-induced hyperpolarization of the mammalian muscle cell.

Extracellularly applied vanadyl (IV) hyperpolarized the membrane potential of mouse diaphragm muscle from about -74.0 mV up to -81.7 mV. The hyperpolarizing effect of 10(-4) mol.I-1 vanadyl (IV) is comparable with hyperpolarization induced by 100 mU.ml-1 insulin. Both compounds increased the intracellular K+ concentration, the hyperpolarizing effect of vanadyl (IV) and insulin is blocked by ouabain and is unaffected by removal of K+ from the external medium. Triggering of the release of intracellular K+ associated with cellular proteins is proposed as the mechanism of vanadyl (IV) and insulin-induced hyperpolarization.

Animals↗

PubMed2006

Petroleum contaminated soil in Oman: evaluation of bioremediation treatment and potential for reuse in hot asphalt mix concrete.

This paper presents a study that aims at evaluating the leaching characteristics of petroleum contaminated soils as well as their application in hot mix asphalt concrete. Soil samples are environmentally characterized in terms of their total heavy metals and hydrocarbon compounds and leachability. The total petroleum hydrocarbon (TPH) present in the PCS before and after treatment was determined to be 6.8% and 5.3% by dry weight, indicating a reduction of 1% in the TPH of PCS due to the current treatment employed. Results of the total heavy metal analysis on soils indicate that the concentrations of heavy metals are lower when extraction of the soil samples is carried out using hexane in comparison to TCE. The results show that the clean soils present in the vicinity of contaminated sites contain heavy metals in the following decreasing order: nickel (Ni), followed by chromium (Cr), zinc (Zn), copper (Cu), lead (Pb), and vanadium (V). The current treatment practice employed for remediation of the contaminated soil reduces the concentrations of nickel and chromium, but increases the concentrations of all remaining heavy metals.

Biodegradation, Environmental↗

PubMed1990

Some selected haematological indices in Wistar rats in the vanadium-ethanol interaction.

1. Wistar rats of both sexes daily received an ethanol solution of ammonium metavanadate (AMV) of 0.3 mg V/cm3 5% ethanol concentration as sole drinking liquid, for a period of 4 weeks. 2. The reference groups received for drinking aqueous AMV solution, or 5% ethanol, or water. 3. In animals drinking both water and ethanol AMV solution a decrease in the erythrocyte count and haemoglobin level was noted together with an increase of the percentage of reticulocytes and polychromatophilic erythrocytes in the peripheral blood. 4. A small rise of the percentage of polychromatophilic and orthochromatic erythroblasts was at the same time noted in the bone marrow of animals receiving ethanol AMV solution. 5. In the group of animals drinking 5% ethanol a fall of the erythrocyte count was observed and a rise of the leukocyte count, particularly of lymphocytes. 6. Substitution of water by 5% ethanol solution as solvent for AMV did not have any distinct influence on the toxicity of the tested compound.

Animals↗

PubMed2005

Interactions of vanadium(V)-citrate complexes with the sarcoplasmic reticulum calcium pump.

Among the biotargets interacting with vanadium is the calcium pump from the sarcoplasmic reticulum (SR). To this end, initial research efforts were launched with two vanadium(V)-citrate complexes, namely (NH(4))(6)[V(2)O(4)(C(6)H(4)O(7))(2)].6H(2)O and (NH(4))(6)[V(2)O(2)(O(2))(2)(C(6)H(4)O(7))(2)].4H(2)O, potentially capable of interacting with the SR calcium pump by combining kinetic studies with (51)V NMR spectroscopy. Upon dissolution in the reaction medium (concentration range: 4-0.5mM), both vanadium(V):citrate (VC) and peroxovanadium(V):citrate (PVC) complexes are partially converted into vanadate oligomers. A 1mM solution of the PVC complex, containing 184microM of the PVC complex, 94microM oxoperoxovanadium(V) (PV) species, 222microM monomeric (V1), 43microM dimeric (V2) and 53microM tetrameric (V4) species, inhibits Ca(2+) accumulation by 75 %, whereas a solution of the VC complex of the same vanadium concentration, containing 98microM of the VC complex, 263microM monomeric (V1), 64microM dimeric (V2) and 92microM tetrameric (V4) species inhibits the calcium pump activity by 33 %. In contrast, a 1 mM metavanadate solution, containing 460microM monomeric (V1), 90.2microM dimeric (V2) and 80microM tetrameric (V4) species, has no effect on Ca(2+) accumulation. The NMR signals from the VC complex (-548.0ppm), PVC complex (-551.5ppm) and PV (-611.1ppm) are broadened upon SR vesicle addition (2.5mg/ml total protein). The relative order for the half width line broadening of the NMR signals, which reflect the interaction with the protein, was found to be V4>PVC>VC>PV>V2=V1=1, with no effect observed for the V1 and V2 signals. Putting it all together the effects of two vanadium(V)-citrate complexes on the modulation of calcium accumulation and ATP hydrolysis by the SR calcium pump reflected the observed variable reactivity into the nature of key species forming upon dissolution of the title complexes in the reaction media.

Animals↗

PubMed2004

Vanadium bromoperoxidase-catalyzed biosynthesis of halogenated marine natural products.

Marine red algae (Rhodophyta) are a rich source of bioactive halogenated natural products. The biogenesis of the cyclic halogenated terpene marine natural products, in particular, has attracted sustained interest in part because terpenes are the biogenic precursors of many bioactive metabolites. The first enzymatic asymmetric bromination and cyclization of a terpene, producing marine natural products isolated from red algae, is reported. Vanadium bromoperoxidase (V-BrPO) isolated from marine red algae (species of Laurencia, Plocamium, Corallina) catalyzes the bromination of the sesquiterpene (E)-(+)-nerolidol producing alpha-, beta-, and gamma-snyderol and (+)-3beta-bromo-8-epicaparrapi oxide. alpha-Snyderol, beta-snyderol, and (+)-3beta-bromo-8-epicaparrapi oxide have been isolated from Laurencia obtusa, and each have also been isolated from other species of marine red algae. gamma-Snyderol is a proposed intermediate in other bicyclo natural products. Single diastereomers of beta-snyderol, gamma-snyderol, and mixed diastereomers of (+)-3beta-bromo-8-epicaparrapi oxide (de = 20-25%) are produced in the enzyme reaction, whereas two diastereomers of these compounds are formed in the synthesis with 2,4,4,6-tetrabromocyclohexa-2,5-dienone (TBCO). V-BrPO likely functions by catalyzing the two-electron oxidation of bromide ion by hydrogen peroxide producing a bromonium ion or equivalent in the active site that brominates one face of the terminal olefin of nerolidol. These results establish V-BrPO's role in the biosynthesis of brominated cyclic sesquiterpene structures from marine red algae for the first time.

Animals↗

PubMed1983

ESR spectra of VO2+ ions adsorbed on calcium phosphates.

The ESR spectra of oxovanadium(IV) ions, (VO2+), adsorbed on hydroxyapatite(OHAp), fluorhydroxyapatite(FHAp), Mg-containing tricalcium phosphate(Mg-TCP), .octacalcium phosphate (OCP), dicalcium phosphate dihydrate (DCPD), and amorphous calcium phosphate(ACP) were measured at room temperature. The ESR parameters of VO2+ adsorbed on these compounds were slightly different from one another and accordingly, the ESR technique by use of VO2+ was useful for an analysis of the calcium phosphates precipitated from supersaturated solutions. The ESR parameters of VO2+ adsorbed on ACP and Mg-TCP were found to be very similar to each other, suggesting that ACP and TCP resemble each other in the structure of their crystal surfaces.

Adsorption↗

PubMed1997

Insulin-like effects on liver Golgi membrane preparations of bis(oxalato)oxovanadate(IV) complex ion, a new vanadate compound.

Recent studies have shown the insulin-like effect of vanadyl sulphate or sodium ortho (or meta-)vanadate administered orally to rats. Toxicity of these drugs and reluctance by the animals to drink the solutions and take food, concerning the amelioration of some diabetes syndrome discussed in 1994 by Domingo et al. (1), McNeill et al. (2) and Wiliams and Malabu (3), prompted us to investigate a new vanadate complex: disodium bis(oxalato)oxovanadate (IV), Na2[VO(OX)2]H2O. The main object of the experiment was to study whether this complex administered as 3 mmol/l solution in 0.5% NaCl during 7 days could act on the subcellular level and influence the activity of liver Golgi membrane galactosyltransferase activity. Free blood sugar level was lowered (but was still higher than in the control group) in diabetic rats after seven days of vanadate action and was accompanied by lowered, however not statistically significant, serum triglyceride levels. The yields of isolated Golgi-rich membrane fractions were about half of the level in diabetic groups (untreated and treated with vanadium) compared with the control groups. Purity of these membrane fractions, expressed as nmol Gal transferred per mg of proteins and per h, was the same in four groups investigated and showed the possibility to compare them. Activity of galactosyltransferase calculated in nmol Gal transferred per 1 g of liver and per 1 h or per whole liver in the same time (as a possibility of glycosylation of the secretory and membrane glycoproteins) was lower in both diabetic groups. However, after vanadium treatment (D+V group), the activity was higher than in untreated diabetic rats (D group) in three of five investigated animals. Vanadyl-oxalate complex did not normalize in a statistically significant manner the enzyme activity which was significantly lower in diabetes than in control. This is similar to insulin influence on the galactosyltransferase activity reported previously by Kaczmarski et al. in 1981 (4) and Kordowiak et al. in 1981 (5).

Animals↗

PubMed1987

Reactions of oxobis(acetylacetonato)-vanadium (IV) with some purine and pyrimidine bases and nucleosides.

A study of the reactions of purine and pyrimidine bases has been initiated with the V(IV) complex [V(O)(acac)2]. Two distinct modes of reaction have been recognized depending on the nature of the base. Simple adduct formation occurs when the base contains a sufficiently basic lone pair, but when bases contain acidic protons bound to nitrogen (inosine, thymine), cleavage of one acetylacetonate ligand occurs to give potentially polymeric species. This behavior is in contrast to that of the inert [Co(NO2)2(acac)2]-ion.

Nucleosides↗

PubMed1985

Adenosine kinase from bovine adrenal medulla.

Adenosine kinase from bovine adrenal medulla was purified 1600-fold by using ammonium sulfate precipitation, gel filtration and affinity chromatography. Gel filtration yielded a relative molecular mass around 42000 and Michaelis constants were 0.2 microM for adenosine and 20 microM for MgATP. The enzyme showed a broad specificity for purine nucleoside triphosphate as phosphate donors. Both free Mg2+ and ATP were inhibitors. AMP was a competitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP, while ADP was a uncompetitive inhibitor with regard to adenosine and a non-competitive inhibitor versus MgATP. Adenosine kinase was strongly inhibited by the bis(adenylyl) polyphosphates Ap4A and Ap5A. These compounds inhibited the enzyme competitively versus MgATP (Ki = 0.06 microM for Ap4A and 0.4 microM for Ap5A) and uncompetitively with regard to adenosine. The results of the kinetic analysis suggest an ordered bi-bi mechanism, adenosine being the first substrate. The phosphorylation of adenosine was unaffected in the presence of vanadate ions.

Adenine Nucleotides↗

PubMed2004

Investigation of hydrothermal routes to mixed-metal cerium titanium oxides and metal oxidation state assignment using XANES.

The reaction between TiF(3) or TiO(2) and Ce(3+) in sodium hydroxide solutions yields highly crystalline NaCeTi(2)O(6) at room temperature and under mild hydrothermal conditions (T < or = 240 degrees C). There is no evidence for the formation of ternary Ce-Ti-O materials by this method, and the use of bases other than NaOH always produces poorly crystalline materials. The material NaCeTi(2)O(6) has a distorted perovskite structure with sodium and cerium ions randomly occupying the A sites: Pnma, a = 5.4517(8) A, b = 7.7292(6) A, c =5.4573(3) A. XANES spectroscopy at the Ti K edge and Ce L(III) edge, with reference to crystalline model compounds, reveals that cerium is found solely as Ce(III) and titanium as Ti(IV) in NaCeTi(2)O(6). Isomorphous substitution of Ce(3+) by Nd(3+) or Ti(4+) by V(4+) is found to be very facile under hydrothermal conditions (at a temperature of 240 degrees C), by addition of appropriate amounts of metal salts to the hydrothermal reaction mixtures. The series NaCe(1-x)Nd(x)Ti2O6 (0 < or = x < or = 1) and NaCeTi(2-x)V(x)O6 (0 <or = x < or = 1.8) can be formed directly in one step, and all materials were characterized by powder X-ray diffraction. The oxidation states of the substituent elements were determined using XANES spectroscopy, which further demonstrates that isomorphous substitution has taken place, with all vanadium present as V(IV) when the B site is substituted. Scanning electron microscopy analysis of the solids shows them to be made up of irregularly shaped particles made up of clusters of submicron-sized crystallites but that on firing in excess of 1000 degrees C the particle size is increased to approximately 10 microm and the particles have distinct, sharp edges.

Journal Article↗