Vanadate orthovanadate

Determination of vanadium as silver vanadate Discussion. Vanadates are precipitated by excess of silver nitrate solution in the presence of sodium acetate after boiling, the precipitate consists of silver orthovanadate. The following reactions occur with a solution of a metavanadate ... 

It has been stated that the results obtained by precipitation of vanadate as silver orthovanadate Ag3V04 are not altogether satisfactory. Better results are obtained by precipitation at pH 4.5 as silver metavanadate AgV03 the precipitate is weighed after drying at 100-105 °C. 

Vanadate (sodium orthovanadate or peroxovanadate) exhibits insulin-like effects in vitro (activation of insulin receptor tyrosine kinase, PI 3-kinase, Akt) and in vivo (diabetic rats, humans). These effects can be explained at least in part by the inhibition of phosphotyrosine phosphatases which deactivate the INSR tyrosine kinase. 

Vanadates For the isostructural strontium and barium ortho-vanadates the V-—0 vibrational frequencies decrease with increasing effective nuclear charge [51]. Similar orthovanadates with the apatite structure have for a given halogen ion decreasing frequencies of the VO4 ion in the order Ca>Sr >Ba ((62) and Table 4]. However, it is impossible to see any trend towards the tiivalent lanthanide cations (59). The IR bands are so wide in this case that small changes cannot be measured. 

The vanadate(V) anions give rise to numerous salts. Among the most common are the orthovanadates (V04 ), metavanadates and... 

This paper summarized our current understanding of the factors that determine selectivity for dehydrogenation versus formation of oxygen-containing products in the oxidation of light alkanes. From the patterns of product distribution in the oxidation of C2 to C6 alkanes obtained with supported vanadium oxide, orthovanadates of cations of different reduction potentials, and vanadates of different bonding units of VO in the active sites, it was shown that the selectivities can be explained by the probability of the surface alkyl species (or the... 

Silver orthovanadate reacts with alkyl halides to give esters of vanadic acid. These are yellow liquids of general formula Alk.3V04, in which Aik. represents the alkyl radical. Esters of orthovanadic acid axe more stable than those of pyro- and meta-vanadic acids that is, the order of stability is the reverse of that which applies to the inorganic salts.3 The following orthovanadates have been prepared —... 

Bismuth Orthovanadate, BiV04, is a bright yellow compound obtained by the double decomposition of bismuth nitrate with an alkali vanadate.4... 

Pyrovanadates, R 4V207 or 2R a0.Va05.—The alkali pyrovana-dates are prepared by dissolving the equivalent quantity of vanadium pentoxide in solutions of alkalis, or by the spontaneous decomposition in solution of the alkali orthovanadates. Pyrovanadates of other metals are obtained by fusing vanadium pentoxide with the salts or hydroxides of the metals in molecular proportions, or, when they are sufficiently insoluble, by double decomposition between an alkali pyro-vanadate and a salt of the metal required. 

The solution chemistry of the rare earth vanadates has received considerable attention [359,360]. It has been found that when ammonium metavanadate solution is added to rare earth nitrate solutions, an increase in acidity results with the formation of the orthovanadates (eq. 35). However, when the solutions are mixed in the opposite order the pH of the medium remains unchanged and precipitates of metavanadates the (eq. 36) are produced. 

Vanadate. Sodium vanadate, sodium orthovanadate, Na3V04, white solid, soluble, formed by fusion of vanadium pentoxide and sodium carbonate. Used (1) in inks, (2) in photography, (3) in dyeing of furs, (4) in inoculation of plant life. 

Other forms of vanadium have been implicated in the stimulation of the plasma membrane vanadate-dependent NAD(P)H oxidation reaction. Decavanadate has been shown to be a more potent stimulator of the vanadate-dependent NADH oxidation activity than added orthovanadate [30,31], Interestingly, decavanadate reductase activity has been found to be an alternative activity of an NADP-specific isocitrate dehydrogenase [32], Diperoxovanadium derivatives have also been shown to be involved in this type of reaction [33,34], Decavanadate may play a role in the biological role of vanadium, as it is found in yeast cells growing in the presence of orthovanadate [8] and is a potent inhibitor of phosphofructokinase-1, the control step of glycolysis, and other metabolic reactions [35],... 

Experiments on the proliferative effects of vanadium compounds are not always clear. Results on the effect of vanadium compound administration on erythropoiesis, or development of red blood cells, have been mixed. A recent report has shown that orthovanadate stimulated erythropoiesis by stimulating the maturation of red blood cell precursors [78], Peroxovanadate addition is reported to stimulate neurite outgrowth in PC12 cells [79], whereas vanadate causes growth inhibition in these cells [70],... 

Willsky, G.R., D.A. White, and B.C. McCabe. 1984. Metabolism of added orthovanadate to vanadyl and high-molecular-weight vanadates by Saccharomyces cerevisiae. J. Biol. Chem. 259 13273-81. 

Five-coordinate pentavalent vanadium has never been actually demonstrated for any enzyme, nor is the state of protonation of the bound vanadate known. While monomeric orthovanadate, or one of its protonated forms, appears to be the species responsible for enzyme inhibition, in a few instances the decavanadate may be involved27,28. In general, caution must be exercised when attributing inhibition to a particular species of vanadate. Which vanadate species are present in solution depends markedly on pH and on concentration and, moreover, equilibrium is usually only slowly achieved. 

Vanadate solutions are usually prepared from sodium orthovanadate, Na3V04, or sodium metavanadate, NaV03, or from the corresponding ammonium salts. These give the same vanadate species in solution after equilibration. In vitro assays of the effect of vanadate reported in the literature have used a wide range of concentrations, ca 10 mM to 1 nM. It is instructive to examine the species of vanadate which are expected to be present under conditions of equilibrium at these concentrations of vanadium. 

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