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PubMed1995

Characterization of V2O5-AlPO4 catalysts by 51V and 1H magic-angle spinning solid-state nuclear magnetic resonance spectroscopy.

Amorphous aluminum orthophosphate is used as a carrier for preparing a series of V2O5-AlPO4 catalysts with varying vanadia content. The catalysts were characterized by solid-state 51V and 1H magic-angle spinning nuclear magnetic resonance (MAS NMR), electron spin resonance (ESR) and X-ray diffraction (XRD). The XRD patterns of the catalysts remained amorphous at all loadings studied. 51V Solid-state NMR spectra revealed the presence of V2O5 microcrystallites at higher vanadia loadings. The 1H MAS NMR spectra of the catalysts showed a maximum consumption of support hydroxyl groups at 6 wt.-% V2O5 indicating the completion of a monolayer at this composition.

Aluminum Compounds↗
PubMed2004

An analysis of candidates for addition to the Clean Air Act list of hazardous air pollutants.

There are 188 air toxics listed as hazardous air pollutants (HAPs) in the Clean Air Act (CAA), based on their potential to adversely impact public health. This paper presents several analyses performed to screen potential candidates for addition to the HAPs list. We analyzed 1086 HAPs and potential HAPs, including chemicals regulated by the state of California or with emissions reported to the Toxics Release Inventory (TRI). HAPs and potential HAPs were ranked by their emissions to air, and by toxicity-weighted (tox-wtd) emissions for cancer and noncancer, using emissions information from the TRI and toxicity information from state and federal agencies. Separate consideration was given for persistent, bioaccumulative toxins (PBTs), reproductive or developmental toxins, and chemicals under evaluation for regulation as toxic air contaminants in California. Forty-four pollutants were identified as candidate HAPs based on three ranking analyses and whether they were a PBT or a reproductive or developmental toxin. Of these, nine qualified in two or three different rankings (ammonia [NH3], copper [Cu], Cu compounds, nitric acid [HNO3], N-methyl-2-pyrrolidone, sulfuric acid [H2SO4], vanadium [V] compounds, zinc [Zn], and Zn compounds). This analysis suggests further evaluation of several pollutants for possible addition to the CAA list of HAPs.

Air Pollutants↗
PubMed2001

Vanadocenes as potent anti-proliferative agents disrupting mitotic spindle formation in cancer cells.

We present experimental data which establish the organometallic compounds vanadocene dichloride (VDC) and vanadocene acetylacetonate (VDacac) as potent anti-proliferative agents. We first examined the effects of VDC and VDacac on the rapid embryonic cell division and development of Zebrafish. Both compounds were capable of causing cell division block at the 8-16 cell stage of embryonic development followed by total cell fusion and developmental arrest. We next examined the effect of VDC and VDacac on proliferation of human breast cancer and glioblastoma cell lines using MTT assays. VDC inhibited the proliferation of the breast cancer cell line BT-20 as well as the glioblastoma cell line U373 in a concentration-dependent fashion with IC50 values of 11.0, 14.9 and 18.6 microM, respectively. VDacac inhibited cellular proliferation with IC50 values of 9.1, 26.9 and 35.5 microM, respectively. Whereas in vehicle-treated control cancer cells mitotic spindles were organized as a bipolar microtubule array and the DNA was organized on a metaphase plate, vanadocene-treated cancer cells had aberrant monopolar mitotic structures where microtubules were detected only on one side of the chromosomes and the chromosomes were arranged in a circular pattern. In contrast to control cells which showed a single focus of gamma-tubulin at each pole of the bipolar mitotic spindle, VDC- or VDacac-treated cells had two foci of gamma-tubulin on the same side of the chromosomes resulting in a broad centrosome at one pole. All monopolar spindles examined had two foci of gamma-tubulin labeling consistent with a mechanism in which the centrosomes duplicate but do not separate properly to form a bipolar spindle. These results provide unprecedented evidence that organometallic compounds can block cell division in human cancer cells by disrupting bipolar spindle formation. In accordance with these results vanadocene treatment caused an arrest at the G2/M phase of the cell cycle. This unique mechanism of anti-mitotic function warrants further development of vanadocene complexes as anti-cancer drugs.

Animals↗
PubMedDate not supplied

Pharmacotherapy of type 2 diabetes mellitus.

OBJECTIVE: To review the drug treatments and some of the popular, nontraditional remedies now available for type 2 diabetes mellitus, as well as selected investigational agents; to describe each medication's place in the overall approach to treatment. DATA SOURCES: English-language journals, abstracts, review articles, and newspaper accounts. DATA SYNTHESIS: In the past five years, there has been tremendous progress in the pharmacotherapy of diabetes, particularly type 2 diabetes. Several new agents have entered the clinical arena, and many more are in the late stages of investigation leading to approval. Sulfonylureas stimulate the production and release of insulin; these drugs must be used in patients with an intact pancreas. The meglitinides are nonsulfonylurea agents that are also insulin secretagogues. Unlike the sulfonylureas, repaglinide appears to require the presence of glucose to close the adenosine triphosphate-sensitive potassium channels and induce calcium influx. Metformin reduces hepatic glucose production in some patients and increases peripheral glucose utilization, but its use is hampered by a high percentage of adverse reactions. Disaccharidase inhibitors effectively compensate for the defective early-phase insulin release by slowing the production of sugars from carbohydrates. Thiazolidinediones appear to activate peroxisome proliferator-activated receptor gamma, which is involved in the metabolism of lipids. Short-acting insulin and the role of weight-loss agents are also discussed. CONCLUSIONS: The availability of new options for diabetes therapy provides a chance for successful therapy in a larger number of patients. However, it is important to consider how much true benefit these new forms of treatment will have on the diabetic community. The best choice for a patient remains controversial.

Anti-Obesity Agents↗
PubMed2006

cis,cis-[(bpy)2RuVO]2O4+ catalyzes water oxidation formally via in situ generation of radicaloid RuIV-O*.

The mechanism of the catalytic oxidation of water by cis,cis-[(bpy)(2)Ru(OH(2))](2)O(4+) to give molecular dioxygen was investigated using Density Functional Theory (DFT). A series of four oxidation and four deprotonation events generate the catalytically competent species cis,cis-[(bpy)(2)Ru(V)O](2)O(4+), which breaks the H-OH bond homolytically at the rate determining transition state to give a hydroperoxo intermediate. Our calculations predict a rate determining activation barrier of 25.9 kcal/mol in solution phase, which is in reasonable agreement with the previously reported experimental estimate of 18.7-23.3 kcal/mol. A number of plausible coupling schemes of the two metal sites including strong coupling, weak ferromagnetic and weak antiferromagnetic coupling have been considered. In addition, both high-spin and low-spin states at each of the Ru(V)-d(3) centers were explored and we found that the high-spin states play an important mechanistic role. Our calculations suggest that cis,cis-[(bpy)(2)Ru(V)O](2)O(4+) performs formally an intramolecular ligand-to-metal charge transfer when reacting with water to formally give a cis,cis-[(bpy)(2)Ru(IV)O*](2)O(4+) complex. We propose that the key characteristic of the diruthenium catalyst that allows it to accomplish the most difficult first two oxidations of the overall four-electron redox reaction is directly associated with this in situ generation of two radicaloid oxo moieties that promote the water splitting reaction. A proton coupled metal-to-metal charge transfer follows to yield a Ru(V)/Ru(III) peroxo/aqua mixed valence complex, which performs the third redox reaction to give the superoxo/aqua complex. Finally, intersystem crossing to a ferromagnetically coupled Ru(IV)/Ru(III) superoxo/aqua species is predicted, which will then promote the last redox event to release triplet dioxygen as the final product. A number of key features of the computed mechanism are explored in detail to derive a conceptual understanding of the catalytic mechanism.

2,2'-Dipyridyl↗
PubMed1998

[Genotoxic effects of vanadyl sulfate in Drosophila melanogaster].

This study presents the analysis of chemically induced somatic mutation in Drosophila larvae assayed later as single light (LS) mosaic spots in the adult eye. The larvae were treated with Vanadyl sulphate (VOSO4), the highest exposure was 10.0, 8.0, 6.0 and 4.0 mM which was the acutely lethal concentration, while than lowest exposure of 2.5, 2.0 and 1.0 mM, cause reproductive effects and genotoxic activity, compared to the control. Previous to the realization of the mutagenicity assay was determined the lethal toxicity of the compound undertest since the concentration-mortality relationship is a useful indicator of the biological activity of Vanadium. The toxic effect in fly adult was to compare any differences in the sensitivity of males (white) and female (oregon), observing the higher sensitivity of the males. The date presented with tests SMART and their statistical evaluation lead to the following conclusions. To test the two hypotheses was propose to apply the conditional binomial test (Kastenbaum and Bowman, 1970) or the X2 test for proportions (K. Pearson criterion). Each hypothesis was tested at the 5% significance level. In conclusion the Vanadyl Sulphate produce aberrant red sector in w+/w, it is not correlated with the capacity of an agent to induce chromosomal damage and mitotic recombination, but rather seems positively correlated with its weak capacity to produce points mutations.

Animals↗
PubMed1999

Solvent and temperature dependence of spin echo dephasing for chromium(V) and vanadyl complexes in glassy solution.

The solvent and temperature dependence of the rate constant for spin echo dephasing, 1/Tm, for 0.2 to 1.2 mM glassy solutions of chromyl bis(1-hydroxy-cyclohexanecarboxylic acid), CrO(HCA)-2; aquo vanadyl ion, VO2+ (aq), and vanadyl bis(trifluoroacetylacetonate), VO(tfac)2 were examined. At low temperatures where 1/T1 << 1/Tm, 1/Tm in 1:1 H2O:glycerol is dominated by solvent protons. At low temperature 1/Tm increases in the order 1:1 H2O:glycerol or 9:1 CF3CH2OH:ethyleneglycol (no methyl groups) < 9:1 i-PrOH:MeOH (hindered methyl groups) < 9:1 n-PrOH:MeOH (less hindered methyl groups). This solvent dependence of 1/Tm is similar to that observed for nitroxyl radicals, which indicates that the effect of solvent methyl groups on spin-echo dephasing at low temperature is quite general. At higher temperatures the echo dephasing is dominated by spin-lattice relaxation and is concentration dependent. As the glass softens, echo dephasing is dominated by the onset of molecular tumbling.

Chromium↗
PubMed2000

Water and bromide in the active center of vanadate-dependent haloperoxidases.

Two aqua-oxovanadium complexes, viz. [A-VO(H2O)(sal-L-Leu)] (1) and [VO(H2O)2(5-Br-sal-Gly)] x H2O(2 x H2O), containing the water ligands in cis- and trans-positions to the oxo group at V-OH2 distances ranging from 2.008 to 2.228 A, have been structurally characterized in order to model the apical electron density feature found in the structures of fungal and algal vanadate-dependent peroxidases. Br K-edge XAS of bromide-treated bromoperoxidase from Ascophyllum nodosum and model compounds (including 2 x H2O) has been used to show that the substrate bromide does not bind to active site vanadium but to a light atom, possibly carbon, in its vicinity.

Binding Sites↗
PubMed1991

Effectiveness of some chelating agents on distribution and excretion of vanadium in rats after prolonged oral administration.

Vanadium has been shown to have a number of insulin-like effects and has been demonstrated to be beneficial in the treatment of streptozotocin-diabetic rats when included in the drinking water. However, some signs of toxicity and vanadium accumulation in all analysed tissues were reported in vanadium-treated animals. In the present study, the effect of repeated intraperitoneal administration of sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron), ascorbic acid and deferoxamine mesylate (DFOA) or 2-mercaptosuccinic acid on the distribution and excretion of vanadium was determined in male Sprague-Dawley rats. Rats received sodium metavanadate (NaVO3) or vanadyl sulphate pentahydrate (VOSO4.5H2O) in the drinking water at concentrations of 0.15 mg ml-1 (NaVO3) and 0.31 mg ml-1 (VOSO4.5H2O) for 6 weeks. After the end of this exposure period, chelating agents were administered for 2 weeks (3 days per week) at doses approximately equal to one-tenth of their respective LD50. Urine was collected on days 1, 7 and 14 of treatment. Twenty-four hours after the final chelator injection, rats were killed and vanadium concentrations were determined in various tissues. Tiron and DFOA were effective compounds in mobilizing vanadium after NaVO3 administration, whereas Tiron was the most effective chelator after vanadyl sulphate administration. Ascorbic acid neither increased urinary elimination nor decreased tissue vanadium concentrations.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗
PubMed2005

Narrow pore-diameter polypyrrole nanotubes.

Bulk quantities of electrically conducting nanotubes of polypyrrole having narrow pore diameter (6 nm) can be synthesized rapidly by chemical oxidative polymerization of pyrrole in the presence of stoichiometric amounts of V2O5 nanofibers. The V2O5 nanofibers act as templates for polymerization and yield, as the initial product, polypyrrole nanotubes with pores filled with V2O5. The V2O5 dissolves readily in aq. 1.0 M HCl, yielding hollow polypyrrole nanotubes having conductivity of approximately 2 S/cm. As-synthesized polypyrrole nanotubes spontaneously reduce noble metal ions to the corresponding metal nanoparticles at room temperature without any capping or dispersing agents. For example, 3-5 nm size nanoparticles of Ag, Au, and Pd, etc., deposit readily on the surface of the tubes which then migrate spontaneously to the pore, and, in the case of Ag, coalesce in the core, yielding 4-8 nm diameter coaxial cables of Ag surrounded by a 20-30 nm thick polypyrrole fiber sheath.

Chlorides↗
PubMed1998

Model Studies of the Interaction of Vanadium(III) and Oxovanadium(IV/V) with the Carbonyl Amide Oxygen.

A series of vanadium(III) and oxovanadium(IV/V) compounds with the ligands, N-(2-nitrophenyl)pyridine-2-carboxamide (Hpycan), N-(phenyl)pyridine-2-carboxamide (Hpheca), and N-(2-pyridyl)acetamide (Hpyra), containing the amide functionality, was prepared and characterized both in solution and in solid state. All vanadium compounds contain a vanadium-amide oxygen bond. Crystal data for [VOCl(2)(OC(2)H(5))(Hpheca)] (4) are monoclinic; P2(1)/a; a = 12.668(5) Å, b = 8.084(3) Å, c = 17.222(6) Å, alpha = 108.148(12) degrees; Z = 4. In addition to the synthesis and crystallographic studies, the optical, infrared, and magnetic properties of these compounds are reported. Electron paramagnetic resonance [of oxovanadium(IV) species] and (1)H, (13)C{(1)H}, and (51)V nuclear magnetic resonance [of oxovanadium(V) compounds] properties are reported as well.

Journal Article↗
PubMed1999

Bromine K-edge EXAFS studies of bromide binding to bromoperoxidase from Ascophyllum nodosum.

Bromine K-edge EXAFS studies have been carried out for bromide/peroxidase samples in Tris buffer at pH 8. The results are compared with those of aqueous (Tris-buffered) bromide and vanadium model compounds containing Br-V, Br-C(aliphatic) and Br-C(aromatic) bonds. It is found that bromide does not coordinate to the vanadium centre. Rather, bromine binds covalently to carbon. A possible candidate is active site serine.

Bromides↗
PubMed2003

Reactivity of tracheal smooth muscles in albino rats with experimental diabetes mellitus treated with a new complex compound of oxovanadium (IV) and isonicotinic acid hydrazide.

We studied functional properties of tracheal smooth muscle cells in rats with diabetes mellitus. Reactivity of tracheal smooth muscles increased in rats with experimental alloxan-induced diabetes mellitus. A new complex compound of oxovanadium (IV) and isonicotinic acid hydrazide affected reactivity of tracheal smooth muscles in albino rats with experimental type I diabetes mellitus. This new organic vanadium-containing compound reduced contractility of tracheal smooth muscles in rats and potentiated relaxation of smooth muscle cells in the trachea in response to exogenous nitric oxide.

Alloxan↗
PubMed2004

Formation of an oxo-radical of peroxovanadate during reduction of diperoxovanadate with vanadyl sulfate or ferrous sulfate.

Formation of oxygen radicals during reduction of H(2)O(2) or diperoxovanadate with vanadyl sulfate or ferrous sulfate was indicated by the 1:2:2:1 electron spin resonance (ESR) signals of the DMPO adduct typical of standard ()OH radical. Signals derived from diperoxovanadate remained unchanged in the presence of ethanol in contrast to those from H(2)O(2). This gave the clue that they represent a different radical, possibly (*)OV(O(2))(2+), formed on breaking a peroxo-bridge of diperoxovanadate complex. The above reaction mixtures evolved dioxygen or, when NADH was present, oxidized it rapidly which was accompanied by consumption of dioxygen. Operation of a cycle of peroxovanadates including this new radical is suggested to explain these redox activities both with vanadyl and ferrous sulfates. It can be triggered by ferrous ions released from cellular stores in the presence of catalytic amounts of peroxovanadates.

Electron Spin Resonance Spectroscopy↗
PubMed1990

Reaction of vanadium(V) with thiols generates vanadium (IV) and thiyl radicals.

The in vivo toxicity of vanadium(V) has been found to correlate with the depletion of cellular glutathione and related non-protein thiols. With a view to understanding the mechanism for this observation, we have investigated the oxidation of glutathione, cysteine N-acetylcysteine and penicillamine by vanadium(V), using electron spin resonance (ESR) and ESR spin trapping methodology. The spin trap used was 5,5-dimethyl-1-pyrroline 1-oxide (DMPO). It is found that the oxidation of these thiols by vanadium(V) generates the corresponding thiyl radicals and vanadium- (IV) complexes. The results suggest that free radical reactions play a significant role in the depletion of cellular thiols by vanadium(V) and hence in vanadium(V) toxicity.

Electron Spin Resonance Spectroscopy↗