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PubMed2004

DNA modification by oxovanadium(IV) complexes of salen derivatives.

Oxovanadium(IV) complexes of hydroxysalen derivatives have been prepared and tested as DNA reactive agents. The nuclease activity has been investigated under oxidative or reducing conditions, on the basis of the various oxidation states of vanadium: V(III), V(IV) and V(V). In the absence of an activating agent, none of the compounds tested was able to induce cleavage of DNA, whereas in the presence of mercaptopropionic acid (MPA) or Oxone the four complexes induced DNA modifications. Under both conditions, the para-hydroxy complex was found to be the most active compound. Reaction of these salen complexes with DNA occurs essentially at guanine residues and is more efficient in the presence of Oxone than under reducing conditions. The extent of Oxone-mediated DNA oxidation by the four vanadyl complexes was clearly superior to VOSO(4) and was observed without piperidine treatment. EPR studies provided information on the reactive metal-oxo species involved under each conditions and a mechanism of reaction with DNA is discussed.

DNA, Superhelical↗
PubMed1981

Sodium orthovanadate diuresis in rats.

The renal actions of differing doses of sodium orthovanadate were studied in conscious and anesthetized female Wistar rats. In conscious rats, sodium orthovanadate was given by i.v. or i.p. injections or by mouth. The most pronounced renal effects were seen after a 5 mg/kg i.p. injection of sodium orthovanadate. Urine flow and sodium excretion increased approximately 400% and urine osmolality fell from 1108 to 549 mOsmol/kg . H2O. Higher doses of sodium orthovanadate (20, 30 and 50 mg/kg) injected i.p. did not cause diuresis and were toxic. In anesthetized rats undergoing a 0.9% NaCl diuresis, i.v. infusion of sodium orthovanadate at a dose of 5 mg/kg/hr significantly increased urine flow and the excretion of sodium, calcium, phosphorus, sulfur, magnesium and chlorine, whereas glomerular filtration rate was unaltered. In anesthetized rats undergoing a water diuresis, i.v. infusion of sodium orthovanadate (5 mg/kg/hr) markedly reduced free-water clearance, indicating that this compound inhibits tubular reabsorption of sodium and chloride in diluting nephron segments. Blood and renal tissue levels of vanadium, measured using emission spectrographic analysis, in rats infused with sodium orthovanadate were 4 times higher than the concentration of sodium orthovanadate (1--10 microM) needed to inhibit 50% of the Na-K-adenosine triphosphate activity of rat renal homogenates in vitro. These data suggest that sodium orthovanadate produces diuresis at least in part by inhibiting Na-K-adenosine triphosphatase and solute transport in the distal nephron, likely the ascending limb of the loop of Henle.

Administration, Oral↗
PubMed1993

Zymosan-induced tyrosine phosphorylations in human monocytes. Role of protein kinase C.

Protein tyrosine phosphorylations are involved in the proliferation and secretory responses of immune cells, but their role in phagocytes is poorly understood. The ability of unopsonized zymosan to induce protein tyrosine phosphorylations was investigated in human monocytes. The addition of zymosan to monocytes resulted in an increase in tyrosine phosphorylation of several endogenous proteins including 28-, 33-, 38-, 42-, 47-, 55- to 60-, 62-, 68-, 90-, 105-, 116-, and 120-kDa proteins; 55- to 60-kDa proteins were the predominant phosphoproteins. Moreover, we studied the effects of tyrphostin 23, a specific tyrosine kinase inhibitor, on stimulated tyrosine phosphorylations and early secretory responses of monocytes, i.e., arachidonic acid release and oxidative metabolism. We showed that tyrphostin inhibited zymosan-stimulated tyrosine phosphorylations and arachidonic acid release, but that it did not affect superoxide generation induced by zymosan. Zymosan binds mainly to CR3 receptor on human monocytes, and CR3 is devoid of intrinsic tyrosine kinase activity. It was predictable that zymosan stimulated a tyrosine kinase distal to the receptor or associated with it. We observed that PMA mimicked zymosan-induced tyrosine phosphorylations, thus suggesting that both agonists used a common transductional pathway implicating the serine/threonine kinase, protein kinase C. The antagonists of protein kinase C, sphingosine and calphostin C, inhibited zymosan-stimulated tyrosine phosphorylations. We suggest that, in human monocytes, zymosan-induced tyrosine phosphorylations are involved in cell responses such as the release of arachidonic acid, and that they require the sequential activation of protein kinase C and cellular protein tyrosine kinases.

Catechols↗
PubMed1993

Carcinogenicity of trace elements with reference to evaluations made by the International Agency for Research on Cancer.

The monograph program of the International Agency for Research of on Cancer has evaluated many trace elements for their carcinogenicity to humans. Five groups of compounds were considered human carcinogens: arsenic and arsenic compounds, beryllium and beryllium compounds, cadmium and cadmium compounds, hexavalent chromium compounds, and nickel compounds. Antimony trioxide, cobalt and cobalt compounds, lead and inorganic lead compounds, methylmercury compounds, and metallic nickel were considered possibly carcinogenic to humans. Antimony trisulfide, trivalent chromium compounds, metallic chromium, ferric oxide, organolead compounds, metallic mercury, inorganic mercury compounds, selenium and selenium compounds, and titanium dioxide were not classifiable. Trace elements studied to a limited extent include copper, manganese, tin, vanadium, and zinc. Among the problems are the lack of relevant data, the definition of active species, the extrapolation of the results of experimental studies to humans, the methodological problems of epidemiologic studies, and the possible anticarcinogenic activity of some trace elements.

Humans↗
PubMed1997

Syntheses, X-ray Structures, and Solution Properties of [V(4)O(4){(OCH(2))(3)CCH(3)}(3)(OC(2)H(5))(3)] and [V(4)O(4){(OCH(2))(3)CCH(3)}(2)(OCH(3))(6)]: Examples of New Ligand Coordination Modes.

Tetranuclear vanadium complexes with alkoxy ligands, [V(4)O(4){&mgr;,&mgr;,&mgr;(3)-(OCH(2))(3)CCH(3)}(2)(OCH(3))(6)] (1) and [V(4)O(4){&mgr;-(OCH(2))(3)CCH(3)}{&mgr;,&mgr;(3)-(OCH(2))(3)CCH(3)}{&mgr;,&mgr;,&mgr;(3)-(OCH(2))(3)CCH(3)}(OR)(3)] (R = C(2)H(5) (2), R = CH(CH(3))(2) (3), R = CH(3) (4)), were synthesized by reacting VO(OR)(3) and H(3)thme (H(3)thme = 1,1,1-tris(hydroxymethyl)ethane) in alcohol. Complex 1 crystallized in the monoclinic space group P2(1)/n with a = 9.646(4) Å, b = 11.502(3) Å, c = 11.960(3) Å, beta = 90.20(3) degrees, V = 1326.9 (7) Å(3), Z = 2 and R (wR(2)) = 0.045 (0.143). Complex 2 also crystallized in the monoclinic space group P2(1)/n with a = 8.290(8) Å, b = 12.237(2) Å, c = 29.118(4) Å, beta = 89.455(9) degrees, V = 2954(3) Å(3), Z = 4, and R(wR(2)) = 0.049 (0.126). Both 1 and 2 are neutral, discrete complexes possessing a common [V(4)O(16)](12)(-) core, which consists of four vanadium(V) atoms chelated by two (1) or three (2) tridentate thme(3)(-) ligands and by six (1) or three (2) RO(-) groups. Compound 1 exhibits a crystallographically required inversion center; in contrast, complex 2 exhibits no crystallographically imposed symmetry, and its three trialkoxy ligands each coordinate differently (one thme(3)(-) is coordinated in a new coordination mode with the oxygens in a terminal, doubly-bridging and triply-bridging mode). Both compounds 1 and 2 maintain their structures in solution, although compound 1 also forms a second minor species upon dissolution. Sequential exchanges of the RO(-) groups in complexes 2 and 3 were investigated by (51)V and (1)H NMR spectroscopy. For example, [V(4)O(4)(thme)(3)(OC(2)H(5))(3)] will react with CH(3)OH to generate [V(4)O(4)(thme)(3)(OCH(3))(3)] (4). These reactions were found to be reversible. The time scale of the alcohol exchange reactions were found to vary depending on the vanadium center that is undergoing the exchange.

Journal Article↗
PubMed2000

Spin-singlet clusters in the ladder compound NaV2O5

The space group of alpha(')-NaV2O5 turns below T(c) = 34 K from Pmmn with all V sites equivalent, into Fmm2 with three independent vanadium sites per layer. This is incompatible with models of charge ordering into V4+ and V5+. Our structure determination indicates that the phase transition consists of a charge ordering with three distinct valence states, formally V4+, V4.5+, and V5+. The singlet formation is not associated with dimerization on the spin ladder, but with the formation of spin clusters. Finally, we ascribe the quadrupling of the c axis to the large polarizability of the V2O5 skeleton.

Journal Article↗
PubMed1995

Vanadium-diascorbates are strong candidates for endogenous ouabain-like factors in human urine: effects on Na-K-ATPase enzyme kinetics.

Recently, we isolated from the urine of salt-loaded healthy subjects a more polar ouabain-like factor OLF-1 and a more apolar OLF-2, the latter cross-reacted with a digoxin anti-body. They were purified to single compounds with dose-dependent Na-K-ATPase inhibition. Mass-spectroscopy (MS) showed a Mr of around 400 and 1H-NMR- and IR-spectroscopy suggested diascorbic acid salts, i.e., vanadium (V) diascorbates (Mr 403) with similar elution times from RP-HPLC as OLFs. IC50 was 9 x 10(-5)M for VIV-diascorbate as compared to 2 x 10(-6)M for Vv-diascorbate. Enzyme inhibition was non-competitive with respect to sodium and Mg-ATP; p-NPPase assay showed strong inhibition in its E2-configuration. We suggest that V-diascorbates represent endogenous OLFs excreted in human urine.

4-Nitrophenylphosphatase↗
PubMed2004

Determination of vanadium in heavy oils by atomic absorption spectrometry using a graphite furnace coated with tungsten.

A simple and rapid method was established for the direct determination of vanadium in an oil sample using the tungsten-coated graphite-furnace AAS. The interference of the sulfur compound could be suppressed by choosing the ashing temperature. If the sulfur concentration in the sample is diluted to 1.0 wt% or less, the interference can be suppressed. This proposed method should make important contributions to the quality control of petroleum refineries.

Journal Article↗
PubMed2003

Chlorination and cleavage of lignin structures by fungal chloroperoxidases.

Two fungal chloroperoxidases (CPOs), the heme enzyme from Caldariomyces fumago and the vanadium enzyme from Curvularia inaequalis, chlorinated 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-dihydroxypropane, a dimeric model compound that represents the major nonphenolic structure in lignin. Both enzymes also cleaved this dimer to give 1-chloro-4-ethoxy-3-methoxybenzene and 1,2-dichloro-4-ethoxy-5-methoxybenzene, and they depolymerized a synthetic guaiacyl lignin. Since fungal CPOs occur in soils and the fungi that produce them are common inhabitants of plant debris, CPOs may have roles in the natural production of high-molecular-weight chloroaromatics and in lignin breakdown.

Chloride Peroxidase↗
PubMed1987

Intramolecular cross-linking of domains at the active site links A1 and B subfragments of the Ca2+-ATPase of sarcoplasmic reticulum.

Glutaraldehyde treatment of sarcoplasmic reticulum vesicles results in formation of cross-linked Ca2+-ATPase oligomers. Under limiting reaction conditions, where minimal interpolypeptide cross-linking occurs, hydrodynamic properties of the monomer are altered, such that, on sodium dodecyl sulfate-polyacrylamide electrophoresis, the enzyme migrates with an apparent molecular weight of 125,000 (E(125], as compared to the native enzyme (E(110]. The E(125) species was also formed following reaction with other cross-linking bis-aldehydes, with formaldehyde and with a bissuccinimidyl ester. Derivitization resulted in inactivation of ATPase activity and of phosphoprotein formation from Pi. E(125) formation was inhibited by ATP, ADP, AMPPCP, and orthovanadate, and by specific modification of active site Lys-514 with fluorescein-5'-isothiocyanate. Tryptic cleavage patterns of the glutaraldehyde-modified enzyme were consistent with covalent linkage of A1 and B fragments that have been postulated to comprise the phosphorylation and nucleotide-binding domains (MacLennan, D. H., Brandt, C. J., Korczak, B., and Green, N. M. (1985) Nature 316, 696-700). The denaturing detergent, sodium dodecyl sulfate, prevented cross-link formation. Interdomain cross-linking was inhibited by prior modification with either 2,4,6-trinitrobenzene sulfonate, phenylglyoxal, or pyridoxal-5'-phosphate but was unaffected by thiol group modification with iodoacetate or N-ethylmaleimide, suggesting involvement of lysine residues. These findings indicate that intramolecular cross-linking at the active site of the Ca2+-ATPase involves phosphorylation- and ATP-binding domains that are widely separated in the linear sequence.

Adenosine Triphosphate↗
PubMedDate not supplied

Enzymatic cross-linking of a phenolic polymer extracted from the marine alga Fucus serratus.

We have shown that a phenolic polymer (PP) extracted from Fucus serratus can be cross-linked using a vanadium-dependent bromoperoxidase (BPO). The methanol extracted PP was adsorbed to a quartz crystal sensor and the cross-linking was initiated by the addition of BPO, KBr, and H2O2. The decreased dissipation upon addition of the cross-linking agents, as measured with the quartz crystal microbalance with dissipation monitoring (QCM-D) method, was interpreted as intramolecular cross-links were formed between different phloroglucinol units in the PP. With surface plasmon resonance, it was shown that no desorption occurred from the sensor surface during the cross-linking. UV/vis spectroscopy verified the results achieved with QCM-D that all components, i.e., BPO, KBr, and H2O2, were necessary in order to achieve intramolecular oxidative cross-linking of the polymer.

Adsorption↗
PubMed2005

Vibrational and electronic structure of the dinuclear bis(mu-nitrido) vanadium(v) complex [V(N{N"}2)(mu-N)]2: spectroscopic properties of the M2(mu-N)2 diamond core.

The vibrational and electronic structure of the bis(mu-nitrido) bridged complex [V(N{N"}2)(mu-N)]2 (1) (where [N{N"}2](2-)=[(Me3Si)N{CH(2)CH(2)N(SiMe3)}2](2-)) is analyzed. Assignment of the five modes of the V(2)(mu-N)2 core is based on (15)N isotope shifts and a DFT calculation on the calculated structure I which is an exact reproduction of 1. The three Raman active modes of the planar V(2)(mu-N)2 core are found in the Raman spectrum whereas the two IR allowed vibrations are identified in the infrared spectrum. Furthermore, the electronic structure of is described which complements earlier theoretical studies on the reaction pathway leading to 1(V. M. E. Bates, G. K. B. Clentsmith, F. G. N. Cloke, J. C. Green, H. D. L. Jenkin, Chem. Commun., 2000, 927). Based on the MO scheme of I the UV-vis transitions of 1 are assigned.

Electrons↗
PubMed2006

Immobilized cell reactors in mineralization of dicarboxylic acid solid waste.

Dicarboxylic acid solid waste containing phthalic acid, malic acid, quinone, saturated and unsaturated dicarboxylic esters etc., are discharged in huge quantities during the crackdown of benzene over the catalyst vanadium at temperatures greater than 500 degrees C in a dicarboxylic acid manufacturing industry. Concern over the biological effects of these compounds underlines the necessity to treat this solid waste. The role of yeast Saccharomyces cerevisiae and anaerobic mixed bacterial cultures immobilized in activated carbon, in sequential two stage anoxic reactors, were investigated for the degradation of dicarboxylic acid solid waste (DASW). In the first stage, DASW was dissolved in water to yield a concentration of 0.5% w/v and was treated in yeast Saccharomyces cerevisiae immobilized reactor at an optimum residence time of 24 h. The yeast fermented samples were further treated in an upflow anaerobic reactor containing mixed culture immobilized in activated carbon at an Hydraulic Retention Time (HRT) of 0.2076 days at an hydraulic flow rate of 14.6x10(-3 )m(3)/day and Chemical Oxygen Demand (COD) loading rate of 4.3 kg/m(3)/day. The intermediates that were formed during the yeast fermentation and the anaerobic degradation of DASW were characterized by HPLC, proton NMR, C(13) NMR and mass spectrometry.

Adsorption↗
PubMed2005

Synthesis and spectral characterization of ternary complexes of oxovanadium(IV) containing some acid hydrazones and 2,2'-bipyridine.

An interesting series of heterocyclic base adducts of oxovanadium(IV) complexes have been synthesized by the reaction of vanadium(IV) oxide acetylacetonate with some hydrazones (H(2)L) in the presence of a heterocyclic base 2,2'-bipyridine. The compounds were characterized by analytical and different physico-chemical techniques like IR, electron paramagnetic resonance (EPR) and UV-Vis spectral studies and magnetic studies. The EPR spectra indicate that the free electron is in the d(xy) orbital. The coordination geometry around oxovanadium(IV) in all complexes is octahedral, with one dibasic tridentate ligand L(2-), and one bidentate heterocyclic base. The IR spectra suggest that coordination takes place through azomethine nitrogen and enolate oxygen from the hydrazide moiety and phenolate oxygen. The pyridyl nitrogens of the hydrazones, H(2)L(2) and H(2)L(4) are not involved in the coordination. The molar conductivities show that all the complexes are non-electrolytes. All electronic transitions were assigned. All the compounds are paramagnetic. EPR studies of all compounds suggest axial symmetry. The calculated bonding parameters indicate that in-plane sigma bonding is more covalent than in-plane pi bonding.

2,2'-Dipyridyl↗