Metals and other elements. Wet oxidation method for the determination of submicrogram quantities of mercury in cereal grains.
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Edible Grain↗
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Cellular retention, cytotoxicity and morphological transformation by vanadium(IV) and vanadium(V) in BALB/3T3 cell lines.
Cytotoxicity, morphological transformation and cellular retention have been studied in BALB/3T3 Cl A 31-1-1 cells for ammonium or sodium vanadate [vanadium(V)] and for vanadyl sulphate [vanadium(IV)]. A morphological transformation focus assay showed transforming activity for vanadium(V) (P less than 0.005 at concentrations of 3 x 10(-6) or higher) while vanadium(IV) was not transforming in the cells. Cytotoxicity was higher for vanadium(V) than for vanadium(IV); this was particularly clear at doses from 5 x 10(-6) to 5 x 10(-5) M. The cellular retention of both vanadate and vanadyl compounds at 24, 48 and 72 h incubation was similar. At concentrations lower than 10(-6) M vanadate, the retention was linear with the dose, while at higher exposures the vanadium taken up by the cells levelled off or slightly decreased. Exposure to 10(-6) M and 10(-5) M vanadium(V) for 3 and 24 h as well as to 10(-6) M for 48 and 72 h yielded greater than 94% vanadium in the cytosol, but exposure to a toxic dose (10(-5) M) for 48 and 72 h yielded 20% vanadium associated with cellular organelles, which suggests that some sites in the cytosol become saturated with vanadium. The corresponding gel-filtration experiments indicate that a redistribution of the element among the cytosol components occurs with time.
Animals↗
Mono- and dinuclear oxovanadium(V)calixarene complexes and their activity as oxidation catalysts.
The background of the investigation is constituted by reactive moieties and intermediates playing relevant roles on the surfaces of vanadiumoxide-based catalysts during the oxygenation/dehydrogenation of organic substrates. With the aim of modeling such species, a series of mono- and dinuclear charged and uncharged vanadium oxo complexes containing p-tert-butylated calix[4]arene and calix[8]arene ligands (denoted H4B and H8B' ', respectively, in the protonated forms) has been synthesized and characterized: PPh4[O=VB] ((PPh41), O=VB(OAc) (2), PPh4[O2V2HB' '] (3), and [mu-O(O=V(OMe))2B(Me2)] (4), where superscripts OAc and Me2 indicate that one or two protons of H4B are substituted by these residues, respectively. These compounds were analyzed both in solution and by means of single-crystal X-ray crystallography; it turned out that the crystal structures are retained on dissolution (2 changed only from the paco to the cone structure). In the case of 4, it could be shown that the bulk product consists of a mixture of two isomers (4t and 4c) differing in the relative positions of the vanadium-bound methoxy groups. Subsequently, all compounds were tested as catalysts for the oxidation of alcohols with O2. It turned out that the two dinuclear complexes efficiently catalyze the oxidation of 1-phenyl-1-propargyl alcohol and fluorenol; in addition, they even show some activity with respect to the oxidation of dihydroanthracene. This may hint to a higher activity of dinuclear sites on the surfaces of heterogeneous catalysts as well.
Journal Article↗
Complexes of vanadium(III) with L-alanine and L-aspartic acid.
The equilibria of the complexation processes of V(3+) with L-alanine and L-aspartic acid in aqueous solution over a wide pH range (2-10) were studied by potentiometric and spectroscopic (UV-Vis, CD) methods. The results show that alanine forms complexes with V(3+) in the metal ion concentration range and at the ligand-to-metal ratios investigated, giving mononuclear species only. In ML(2) species, which dominate in the range pH 4-8, alanine acts as a bidendate ligand through O and N atoms. The complexation processes of V(3+) with aspartic acid are more complicated. In acidic solution (up to pH approximately 4) they are similar to those for alanine. In the higher pH region, however, there are complicated equilibria among mono- and various dinuclear species. These dinuclear species consist of carboxylic or mu-oxo bridges and differ from each other by the number of coordinated ligands and OH(-) groups. The solid phase of the V(III) complex with aspartic acid could be isolated from nonaqueous solution only. Spectroscopic (UV-Vis-IR) measurements and magnetic susceptibility data confirm the coordination of vanadium(III) by two carboxylic groups. Both V(III)-L-aspartic acid and V(III)-L-alanine complexes have a significant apoptotic effect on Hepatoma Morris 5123 cells.
Alanine↗
A hydrothermal investigation of the 1/2V2O5-H2C2O4/H3PO4/NH4OH system: synthesis and structures of (NH4)VOPO(4).1.5H2O, (NH4)0.5VOPO(4).1.5H2O, (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2](2).3H2O, and (NH4)2[VO(HPO4)]2(C2O4).5H2O.
The 1/2V2O5-H2C2O4/H3PO4/NH4OH system was investigated using hydrothermal techniques. Four new phases, (NH4)VOPO(4).1.5H2O (1), (NH4)0.5VOPO(4).1.5H2O (2), (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O (3), and (NH4)2[VO(HPO4)]2(C2O4).H2O (4), have been prepared and structurally characterized. Compounds 1 and 2 have layered structures closely related to VOPO(4).2H2O and A0.5VOPO4.yH2O (A = mono- or divalent metals), whereas 3 has a 3D open-framework structure. Compound 4 has a layered structure and contains both oxalate and phosphate anions coordinated to vanadium cations. Crystal data: (NH4)VOPO(4).1.5H2O, tetragonal (I), space group I4/mmm (No. 139), a = 6.3160(5) A, c = 13.540(2) A, Z = 4; (NH4)0.5VOPO(4).1.5H2O, monoclinic, space group P2(1)/m (No. 11), a = 6.9669(6) A, b = 17.663(2) A, c = 8.9304(8) A, beta = 105.347(1) degrees, Z = 8; (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O, triclinic, space group P1 (No. 2), a = 10.2523(9) A, b = 12.263(1) A, c = 12.362(1) A, alpha = 69.041(2) degrees, beta = 65.653(2) degrees, gamma = 87.789(2) degrees, Z = 2; (NH4)2[VO(HPO4)]2(C2O4).5H2O, monoclinic (C), space group C2/m (No. 12), a = 17.735(2) A, b = 6.4180(6) A, c = 22.839(2) A, beta = 102.017(2) degrees, Z = 6.
Journal Article↗
Vanadium haloperoxidase-catalyzed bromination and cyclization of terpenes.
Marine red algae (Rhodophyta) are a rich source of bioactive halogenated natural products, including cyclic terpenes. The biogenesis of certain cyclic halogenated marine natural products is thought to involve marine haloperoxidase enzymes. Evidence is presented that vanadium bromoperoxidase (V-BrPO) isolated and cloned from marine red algae that produce halogenated compounds (e.g., Plocamium cartilagineum, Laurencia pacifica, Corallina officinalis) can catalyze the bromination and cyclization of terpenes and terpene analogues. The V-BrPO-catalyzed reaction with the monoterpene nerol in the presence of bromide ion and hydrogen peroxide produces a monobromo eight-membered cyclic ether similar to laurencin, a brominated C15 acetogenin, from Laurencia glandulifera, along with noncyclic bromohydrin, epoxide, and dibromoproducts; however, reaction of aqueous bromine with nerol produced only noncyclic bromohydrin, epoxide, and dibromoproducts. The V-BrPO-catalyzed reaction with geraniol in the presence of bromide ion and hydrogen peroxide produces two singly brominated six-membered cyclic products, analogous to the ring structures of alpha and beta snyderols, brominated sesquiterpenes from Laurencia, spp., along with noncyclic bromohydrin, epoxide, and dibromoproducts; again, reaction of geraniol with aqueous bromine produces only noncyclic bromohydrin, epoxide, and dibromoproducts. Thus, V-BrPO can direct the electrophilic bromination and cyclization of terpenes.
Catalysis↗
Biochemical and cross-resistance studies with HeLa cell mutants resistant to cardiac glycoside SC4453. Regulation of the resistant form of Na+/K+-ATPase in the mutant cells.
In HeLa cells, stable mutants which are between 25-to about 200-fold resistant to the cardiac glycoside derivative SC4453 (a digoxin analog which contains a pyridazine ring in place of a lactone ring in the C-17 position) have been isolated after a single step selection in the presence of the drug. Based on their cross-resistance pattern towards various cardiac glycosides, the mutants resistant to SC4453 (SCR mutants) appear to be of two different kinds and they differ from the two classes of ouabain-resistant mutants described previously (Gupta, R. S., and Chopra, A. (1985) J. Biol. Chem. 260, 6843-6850). One type of SCR mutants (designated as group C) exhibit a high degree of cross-resistance to all cardiac glycosides and their genins (viz. ouabain, digitoxin, digoxin, digoxigenin, convallatoxin, gitoxin, strophanthidin, and bufalin). In contrast, the second type of SCR mutant (group D) exhibit considerable resistance to only SC4453, digoxin, and digoxigenin, but showed very little or no cross-resistance to the other cardiac glycosides examined. The cross-resistance of the mutants towards cardiac glycosides was highly specific as they exhibited no cross-resistance towards a large number of other structurally and functionally related compounds (viz. ethacrynic acid, sanguinarine nitrate, penicillic acid, methyl quinolizinum bromide, 5,5'-diphenylhydantoin, deoxycorticosterone, vanadium pentoxide, and adriamycin). The cellular uptake of 86Rb in the mutant cells was found to be resistant to specific cardiac glycosides. Studies on the sensitivity of plasma membrane Na+/K+-ATPase to cardiac glycosides show that about 10-15% of the enzymic activity in the mutant cells was highly resistant to inhibition by the specific drugs to which the mutants exhibit increased resistance. Very interestingly, when the mutant cells are grown in cardiac glycoside-containing medium, the resistant form of the enzyme accounts for about 50-60% of the total enzyme. These results show that both classes of SCR mutants are affected in Na+/K+-ATPase and that the amount of the resistant enzyme in the mutant cells is regulated in response to cardiac glycosides.
Cardiac Glycosides↗
Recycling of agricultural solid waste, coir pith: removal of anions, heavy metals, organics and dyes from water by adsorption onto ZnCl2 activated coir pith carbon.
The abundant lignocellulosic agricultural waste, coir pith is used to develop ZnCl(2) activated carbon and applied to the removal of toxic anions, heavy metals, organic compounds and dyes from water. Sorption of inorganic anions such as nitrate, thiocyanate, selenite, chromium(VI), vanadium(V), sulfate, molybdate, phosphate and heavy metals such as nickel(II) and mercury(II) has been studied. Removal of organics such as resorcinol, 4-nitrophenol, catechol, bisphenol A, 2-aminophenol, quinol, O-cresol, phenol and 2-chlorophenol has also been investigated. Uptake of acidic dyes such as acid brilliant blue, acid violet, basic dyes such as methylene blue, rhodamine B, direct dyes such as direct red 12B, congo red and reactive dyes such as procion red, procion orange were also examined to assess the possible use of the adsorbent for the treatment of contaminated ground water. Favorable conditions for maximum removal of all adsorbates at the adsorbate concentration of 20 mg/L were used. Results show that ZnCl(2) activated coir pith carbon is effective for the removal of toxic pollutants from water.
Adsorption↗
Interaction of oxo-bridged vanadium(III) phenanthroline and bipyridine dimers with DNA.
Cationic mu-oxo V(III) dimers of the type [V2OL4Cl2]2+ (L = 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline; or 2,2'-bipyridine) are shown to interact very strongly with DNA and to lead ultimately to its degradation. Spectroscopic binding studies, electrophoreses, DNA melting temperature experiments, and other tests on the parent 1,10-phenthroline complex all yield results consistent with tight binding. However, the exact nature of the binding--i.e., intercalative, groove binding, electrostatic, or covalent--remains unclear. Resonance Raman spectroscopy is found to be a powerful method for studying the interaction of these mu-oxo V(III) dimers with DNA and shows that in frozen aqueous solution, the parent complex [V2O(phen)4Cl2]2+ undergoes initial aquation, followed by the reaction of the aquated species with the DNA. Once the V(III) dimer is bound to the DNA, redox takes place, leading to the formation of alkaline-sensitive lesions. Hydrogen peroxide is implicated as a partner in this redox event, based on the effects of the enzymes SOD and catalase.
Animals↗
Single- and double-cubane clusters in the multiple oxidation states [VFe(3)S(4)](3+,2+,1+).
A new series of cubane-type [VFe(3)S(4)](z)() clusters (z = 1+, 2+, 3+) has been prepared as possible precursor species for clusters related to those present in vanadium-containing nitrogenase. Treatment of [(HBpz(3))VFe(3)S(4)Cl(3)](2)(-) (2, z = 2+), protected from further reaction at the vanadium site by the tris(pyrazolyl)hydroborate ligand, with ferrocenium ion affords the oxidized cluster [(HBpz(3))VFe(3)S(4)Cl(3)](1)(-) (3, z = 3+). Reaction of 2 with Et(3)P results in chloride substitution to give [(HBpz(3))VFe(3)S(4)(PEt(3))(3)](1+) (4, z = 2+). Reaction of 4 with cobaltocene reduced the cluster with formation of the edge-bridged double-cubane [(HBpz(3))(2)V(2)Fe(6)S(8)(PEt(3))(4)] (5, z = 1+, 1+), which with excess chloride underwent ligand substitution to afford [(HBpz(3))(2)V(2)Fe(6)S(8)Cl(4)](4)(-) (6, z = 1+, 1+). X-ray structures of (Me(4)N)[3], [4](PF(6)), 5, and (Et(4)N)(4)[6] x 2MeCN are described. Cluster 5 is isostructural with previously reported [(Cl(4)cat)(2)(Et(3)P)(2)Mo(2)Fe(6)S(8)(PEt(3))(4)] and contains two VFe(3)S(4) cubanes connected across edges by a Fe(2)S(2) rhomb in which the bridging Fe-S distances are shorter than intracubane Fe-S distances. Mössbauer (2-5), magnetic (2-5), and EPR (2, 4) data are reported and demonstrate an S = 3/2 ground state for 2 and 4 and a diamagnetic ground state for 3. Analysis of (57)Fe isomer shifts based on an empirical correlation between shift and oxidation state and appropriate reference shifts results in two conclusions. (i) The oxidation 2 --> 3 + e(-) results in a change in electron density localized largely or completely on the Fe(3) subcluster and associated sulfur atoms. (ii) The most appropriate charge distributions are [V(3+)Fe(3+)Fe(2+)(2)S(4)](2+) (Fe(2.33+)) for 1, 2, and 4 and [V(3+)Fe(3+)(2)Fe(2+)S(4)](3+) (Fe(2.67+)) for 3 and [V(2)Fe(6)S(8)(SEt)(9)](3+). Conclusion i applies to every MFe(3)S(4) cubane-type cluster thus far examined in different redox states at parity of cluster ligation. The formalistic charge distributions are regarded as the best current approximations to electron distributions in these delocalized species. The isomer shifts require that iron atoms are mixed-valence in each cluster.
Catalysis↗
Relationships of toxicological effects to chemical forms of inorganic compounds.
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Animals↗
[Cytostatic non-platinum metal complexes: new perspectives for the treatment of cancer?].
Non-platinum-group metal antitumor agents are represented by inorganic and organometallic compounds which contain either main-group metals such as gallium, germanium, and tin, or transition metals such as titanium, vanadium, iron, copper, and gold. Their antiproliferative properties have been detected during the past years, the spectrum of antitumor activity not being identical with that of cytostatic platinum complexes. In the case of germanium complexes, the antitumor activity is obviously not based on direct cytotoxic effects, but on host-mediated immunopotentiating mechanisms. The toxic properties of most non-platinum-group metal antitumor agents differ fundamentally from those of platinum compounds. Thus, non-platinum-group metal antitumor agents may open new perspectives for the clinical therapy of human malignancies.
Animals↗
In vivo effects of peroxovanadium compounds in BB rats.
Peroxovanadium compounds, each containing an oxo ligand, one or two peroxo anions, and an ancillary ligand in the inner coordination sphere of vanadium, were synthesized, crystallized and characterized by 51V NMR as > 95% pure. They markedly decreased plasma glucose in insulin-deprived diabetic BB rats, with a nadir occurring between 60 and 100 min after intravenous, intraperitoneal or subcutaneous administration. Plasma glucose was reduced after oral administration in insulin-treated and in insulin-deprived BB rats. When compared to sodium orthovanadate, peroxovanadium compounds exhibited a markedly greater potency on a molar basis, and in relation to their toxicity. The in vivo potency can be predicted by the degree of phosphotyrosine phosphatase inhibition observed in vitro. These are the first agents other than insulin that can acutely and markedly reduce plasma glucose in hypoinsulinemic diabetic BB rats.
Animals↗
Vanadium(V) complexes with salicylaldehyde semicarbazone derivatives bearing in vitro anti-tumor activity toward kidney tumor cells (TK-10): crystal structure of [VVO2(5-bromosalicylaldehyde semicarbazone)].
As a contribution to the development of novel vanadium complexes with pharmacologically interesting moieties, new dioxovanadium(V) semicarbazone complexes with the formula cis-VO(2)L, where L=5-bromosalicylaldehyde semicarbazone and 2-hydroxynaphtalen-1-carboxaldehyde semicarbazone have been synthesized and characterized by (1)H and (13)C NMR, Raman and FTIR spectroscopies. Results were compared with those previously reported for other three analogous complexes of this series. The five complexes were tested in three different human tumor cell lines for bioactivity as potential anti-tumor agents, showing selective cytotoxicity on TK-10 cell line. Results showed that structural modifications on the semicarbazone moiety could have a significant effect on the anti-tumor activity of the vanadium complexes. In addition, the electrochemical behavior of all the complexes was studied. No apparent correlation could be demonstrated between reduction potentials of the complexes and their anti-tumor activities. The molecular structure of the novel [V(V)O(2)(5-bromosalicylaldehyde semicarbazone)] complex was solved by X-ray diffraction methods. The vanadium atom shows a distorted square pyramidal coordination sphere. The (VO(2))(+) cation is coordinated to a nearly planar (L)(-) anion acting as a tridentate ligand through both oxygen and one nitrogen atoms.
Aldehydes↗
Vanadate enhances insulin-receptor binding in gestational diabetic human placenta.
Although vanadium is found abundantly in animal and plant kingdoms its biological effects are not clear. Vanadate compounds have been shown to normalize blood glucose levels in streptozotocin treated rats, enhance glucose oxidation and improve the sensitivity to insulin by enhanced receptor binding in rat adipocytes. The aim of the present study was to investigate the effect of vanadate, at high (0-8 mmol l-1) and low (0-1.0 mmol l-1) physiological concentrations, on [125I]-insulin binding in the placenta of three groups of patients, namely from normal (N) controls, gestational diabetics (GDM) and women with risk factors in their medical history for developing diabetes mellitus (RF). Vanadate at low concentrations (0.2-0.6 mmol l-1) enhanced the maximal binding 2-fold in GDM placenta but only increased (up to 1.2-fold) the binding slightly at high concentrations (5 mmol l-1). However with placenta from normal or women at risk, vanadate increased the [125I]-insulin binding up to 1.2-fold both at low and high concentrations. Thus it appears that vanadate augments insulin binding in the placenta from women with gestational diabetes mellitus.
Adult↗
Localizing efficiency of [48V]vanadyl-pheophorbide in tumor as a new tumor imaging agent.
[48V]vanadyl-pheophorbide (48V-Pheo) was synthesized by insertion of 48V into pheophorbide (Pheo), a decomposition product from chlorophyll. At 24 h after injection, 48V-Pheo showed a clearer image of an FM3A tumor than inorganic 48V. This agent also accumulated in MH 134 and S 180 tumors as well as in FM3A tumors. The imaging efficiency was dependent on the affinity of Pheo for tumors. 48V-Pheo seems to be suitable as a tumor imaging agent in conjunction with photodynamic therapy.
Animals↗
Unprecedented [V2O]6+ core of a centrosymmetric thiosemicarbazonato dimer: spontaneous deoxygenation of oxovanadium(IV).
The complex cation [{V(daptsc)(MeOH)}2(mu-O)]2+ [daptsc(2-) = 2,6-diacetylpyridine bis(thiosemicarbazonate)] is the first crystallographically elucidated dimer to possess a [V2O]6+ core, the [V(IV)-O-V(IV)]6+ structural unit, formed by cleavage of the multiple bond in the oxo-cation VO2+, is linear with the oxo group residing on a crystallographic center of inversion, and the temperature dependence of the magnetic data of the dimer is consistent with weak antiferromagnetic coupling of the d1-d1 centers.
Crystallography, X-Ray↗
Synthesis and electrical transport of single-crystal NH4V3O8 nanobelts.
Monoclinic NH(4)V(3)O(8) single-crystalline nanobelts with widths of 80-180 nm, thicknesses of 50-100 nm, and lengths up to tens of micrometers have been synthesized at large scale in an ammonium metavanadate solution by a templates/catalysts-free route. Such nanobelts grow along the direction of [010]. The individual NH(4)V(3)O(8) nanobelt exhibits nonlinear, symmetric current/voltage (I/V) characteristics, with a conductivity of 0.1-1 S/cm at room temperature and a dielectric constant of approximately 130. The dominant conduction mechanism is based on small polaron hopping due to ohmic mechanism at low electric field below 249 V/cm due to Schottky emission at medium electric field between 249 and 600 V/cm and due to the Poole-Frenkel emission mechanism at high field above 600 V/cm.
Catalysis↗