Vanadate

About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.

Microcalorimetric and infrared studies of the acid-base properties of V2O5/γ-Al2O3 catalysts

Abstract: The acid-base properties of V 2 O 5 /γ-Al 2 O 3 catalysts were characterized by ammonia, pyridine and sulphur dioxide adsorptions using microcalorimetry and diffuse reflectance Fourier transform Ir spectroscopy (DRIFT) For vanadium content less than 10 wt-% V 2 O 3 (49 μmol(V 2 O 5 ) m −2 ), the vanadium cations were found to be well spread as vanadate compounds over alumina Such vanadate species developed Bronsted and Lewis-type acidity as shown by a DRIFT spectroscopy study of pyridine adsorption, but did not exhibit a basic character Sulphur dioxide adsorption allowed to differentiate a vanadate layer from free alumina Ammonia and sulphur dioxide adsorptions also showed that at low vanadium coverage, a large part of the vanadate layer was bound to acid-base pairs of alumina Vanadium pentoxide crystallites were detected at less than complete monolayer coverage with vanadate compounds, but did not contribute to the development of the acidic surface character At low vanadium coverage, ( 2 O 5 , 12 μmol(V 2 O 5 ) m −2 ), the acidic character of the V 2 O 5 /γ-Al 2 O 3 catalysts is ascribed to vanadium-free alumina, whereas it is largely attributed to vanadate compounds at higher vanadium coverage

Kinetic Analysis of Proton Transport by the Vanadate-Sensitive ATPase from Maize Root Microsomes

Abstract: Proton transport by the nitrate-insensitive, vanadate-sensitive ATPase in Kl-washed microsomes and reconstituted vesicles from maize (Zea mays L.) roots was followed by changes in acridine orange absorbance in the presence of either KNO(3) or KCl. Data from such studies obeyed a kinetic model in which net proton transport by the pump is the difference between the rate of proton transport by the action of the ATPase and the leak of protons from the vesicles in the direction opposite from the pump. After establishing the steady state proton gradient, the rate of return of transported protons was found to obey first-order kinetics when the activity of the ATPase was completely and rapidly stopped. The rate of return of these protons varied with the quencher used. When the substrate Mg:ATP was depleted by the addition of either EDTA or hexokinase, the rate at which the proton gradient collapsed was faster than when vanadate was used as the quencher. These trends were independent of the anion accompanying the K and the transport assay used.

Peroxovanadates have full insulin-like effects on glycogen synthesis in normal and insulin-resistant skeletal muscle.

Abstract: 1. The insulin-like effects of orthovanadate (10 mM) and peroxides of vanadate (peroxovanadates, at 1 mM) on rates of lactate formation, glucose oxidation and glycogen synthesis were measured in incubated soleus-muscle preparations isolated from non-obese Wistar rats and lean (fa/?) or insulin-resistant obese Zucker (fa/fa) rats. 2. The stimulation of the rates of lactate formation and glucose oxidation by either orthovanadate or peroxovanadates was of similar magnitude to the stimulation by a maximally effective concentration of insulin (1000 microunits/ml). 3. Peroxovanadates, but not orthovanadate, maximally stimulated the rate of glycogen synthesis in incubated soleus muscles isolated from Wistar rats. 4. When soleus-muscle preparations were incubated in the presence of both insulin (1000 microunits/ml) and peroxovanadates (1 mM), this did not result in a synergistic increase in the rate of total glucose utilization as compared with either agent alone. 5. Soleus muscles isolated from obese (fa/fa) Zucker rats exhibited a decrease in response to a physiologically relevant concentration of insulin (100 microunits/ml). Peroxovanadates, at 1 mM, maximally stimulated the rate of glycogen synthesis in soleus muscles isolated from obese (fa/fa) Zucker rats. 6. The findings indicate that peroxovanadates are useful and important agents for investigating the mechanism of action of insulin in skeletal muscle.

High-affinity vanadate transport system in the cyanobacterium Anabaena variabilis ATCC 29413.

Abstract: High-affinity vanadate transport systems have not heretofore been identified in any organism. Anabaena variabilis, which can fix nitrogen by using an alternative V-dependent nitrogenase, transported vanadate well. The concentration of vanadate giving half-maximum V-nitrogenase activity when added to V-starved cells was about 3 × 10−9 M. The genes for an ABC-type vanadate transport system, vupABC, were found in A. variabilis about 5 kb from the major cluster of genes encoding the V-nitrogenase, and like those genes, the vupABC genes were repressed by molybdate; however, unlike the V-nitrogenase genes the vanadate transport genes were expressed in vegetative cells. A vupB mutant failed to grow by using V-nitrogenase unless high levels of vanadate were provided, suggesting that there was also a low-affinity vanadate transport system that functioned in the vupB mutant. The vupABC genes belong to a family of putative metal transport genes that include only one other characterized transport system, the tungstate transport genes of Eubacterium acidaminophilum. Similar genes are not present in the complete genomes of other bacterial strains that have a V-nitrogenase, including Azotobacter vinelandii, Rhodopseudomonas palustris, and Methanosarcina barkeri.