First evidence of mineralization of petroleum asphaltenes by a strain of Neosartorya fischeri

A fungal strain isolated from a microbial consortium growing in a natural asphalt lake is able to grow in purified asphaltenes as the only source of carbon and energy. The asphaltenes were rigorously purified in order to avoid contamination from other petroleum fractions. In addition, most of petroporphyrins were removed. The 18S rRNA and β‐tubulin genomic sequences, as well as some morphologic characteristics, indicate that the isolate is Neosartorya fischeri. After 11 weeks of growth, the fungus is able to metabolize 15.5% of the asphaltenic carbon, including 13.2% transformed to CO₂. In a medium containing asphaltenes as the sole source of carbon and energy, the fungal isolate produces extracellular laccase activity, which is not detected when the fungus grow in a rich medium. The results obtained in this work clearly demonstrate that there are microorganisms able to metabolize and mineralize asphaltenes, which is considered the most recalcitrant petroleum fraction.     

Synthesis of vanadium(IV,V) hydroxamic acid complexes and in vivo assessment of their insulin-like activity

We synthesized vanadyl (oxidation state +IV) and vanadate (oxidation state +V) complexes with the same hydroxamic acid derivative ligand, and assessed their glucose-lowering activities in relation to the vanadium biodistribution behavior in streptozotocin-induced diabetic mice. When the mice received an intraperitoneal injection of the complexes, the vanadate complex more effectively lowered the elevated glucose levels compared with the vanadyl one. The glucose-lowering effect of the vanadate complex was linearly related to its dose within the range from 2.5 to 7.5 mg V/kg. In addition, pretreatment of the vanadate complex induced a larger insulin-enhancing effect than the vanadyl complex. Both complexes were more effective than the corresponding inorganic vanadium compounds. The vanadyl and vanadate complexes, but not the inorganic vanadium compounds, resulted in almost the same organ vanadium distribution. Consequently, the observed differences in the insulin-like activity between the complexes would reflect the potency of the two compounds in the +IV and +V oxidation states in the subcellular region.     

Reduction of vanadium(V) with Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans

Biotechnological leaching has been proposed as a suitable method for extraction of vanadium from spent catalysts and oil ash. In the biological leaching process, the vanadium(V) can be reduced to vanadium(IV), which is a less toxic and more soluble form of the vanadium. The present investigation showed that Acidithiobacillus ferrooxidans efficiently reduced vanadium(V) in the form of vanadium pentaoxide, to vanadyl(IV) ions, and tolerated high concentrations of vanadium(IV) and vanadium(V). A. ferrooxidans was compared with Acidithiobacillus thiooxidans, which has previously been utilized for vanadium leaching and reduction. Vanadium pentaoxide and sodium vanadate were used as model compounds. The results of this study indicate possibilities to develop an economical and technically feasible process for biotechnological vanadium recovery.     

Synthesis of a new vanadyl(IV) complex with trehalose (TreVO): insulin-mimetic activities in osteoblast-like cells in culture

Vanadium compounds show interesting biological and pharmacological properties. Some of them display insulin-mimetic effects and others produce anti-tumor actions. The bioactivity of vanadium is present in inorganic species like the vanadyl(IV) cation or vanadate(V) anion. Nevertheless, the development of new vanadium derivatives with organic ligands which improve the beneficial actions and decrease the toxic effects is of great interest. On the other hand, the mechanisms involved in vanadium bioactivity are still poorly understood. A new vanadium complex of the vanadyl(IV) cation with the disaccharide trehalose (TreVO), Na(6)[VO(Tre)(2)].4H(2)O, here reported, shows interesting insulin-mimetic properties in two osteoblast cell lines, a normal one (MC3T3E1) and a tumoral one (UMR106). The complex affected the proliferation of both cell lines in a different manner. On tumoral cells, TreVO caused a weak stimulation of growth at 5 microM but it inhibited cell proliferation in a dose-response manner between 50 and 100 microM. TreVO significantly inhibited UMR106 differentiation (15-25% of basal) in the range 5-100 microM. On normal osteoblasts, TreVO behaved as a mitogen at 5-25 microM. Different inhibitors of the MAPK pathway blocked this effect. At higher concentrations (75-100 microM), the complex was a weak inhibitor of the MC3T3E1 proliferation. Besides, TreVO enhanced glucose consumption by a mechanism independent of the PI3-kinase activation. In both cell lines, TreVO stimulated the ERK phosphorylation in a dose- and time-dependent manner. Different inhibitors (PD98059, wortmannin, vitamins C and E) partially decreased this effect, which was totally inhibited by their combination. These results suggest that TreVO could be a potential candidate for therapeutic treatments.     

Vanadium(IV/V) speciation of pyridine-2,6-dicarboxylic acid and 4-hydroxy-pyridine-2,6-dicarboxylic acid complexes: potentiometry,EPR spectroscopy and comparison across oxidation states

Evaluation of stability of vanadium(IV) and (V) complexes under similar conditions is critical for the interpretation and assessment of bioactivity of various vanadium species. Detailed understanding of the chemical properties of these complexes is necessary to explain differences observed their activity in biological systems. These studies are carried out to link the chemistry of both vanadium(IV) and (V) complexes of two ligands, 2,6-pyridinedicarboxylic acid (dipicolinic acid, H(2)dipic) and 4-hydroxy-2,6-pyridinedicarboxylic acid (H(2)dipic-OH). Solution speciation of the two 2,6-pyridinedicarboxylic acids with vanadium(IV) and vanadium(V) ions was determined by pH-potentiometry at I=0.2 M (KCl) ionic strength and at T=298 K. The stability and the metal affinities of the ligands were compared. Vanadium(V) complexes were found to form only tridentate coordinated 1:1 complexes, while vanadium(IV) formed complexes with both 1:1 and 1:2 stoichiometries. The formation constant reflects hindered coordination of a second ligand molecule, presumably because of the relatively small size of the metal ion. The most probable binding mode of the complexes was further explored using ambient and low temperature EPR spectroscopy for vanadium(IV) and 51V NMR spectroscopy for vanadium(V) systems. Upon complex formation the pyridinol-OH in position 4 deprotonates with pK approximately 3.7-4.1, which is approximately 6 orders of magnitude lower than that of the free ligand. The deprotonation enhances the ligand metal ion affinity compared to the parent ligand dipicolinic acid. In the light of the speciation and stability data of the metal complexes, the efficiency of the two ligands in transporting the metal ion in the two different oxidation states are assessed and discussed.     

The oxyvanadium constellation in transition-state-analogue complexes of phosphoglucomutase and ribonuclease. Structural deductions from electron-transfer spectra

The absorbance peak in the near ultraviolet electron-transfer spectrum of the oxyvanadium constellation in the "transition-state-analogue complexes" obtained by treating the dephospho form of phosphoglucomutase with inorganic vanadate in the presence of either glucose 1-phosphate or glucose 6-phosphate, as described in an accompanying paper [Ray, W. J., Jr., Burgner, J. W., II, & Post, C. B. (1990) Biochemistry (second of four papers in this issue)], is centered at a wavelength of 312 nm. The position of this peak amounts to a change in oscillator frequency of about -5000 cm-1 relative to that of tetrahedral VO4(3-). To provide a rationale for this spectral change, the near ultraviolet spectra of the di- and monoanions of inorganic vanadate and a number of derivatives of these anions are compared with that of vanadium (V) in the enzymic complexes, in terms of both what is observed experimentally and what is expected from crystal field theory. Comparisons in water and in largely anhydrous solvents show that water is not an essential element in the coordination sphere of inorganic vanadate or its mono- or diesters and hence that the coordination number of V(V) in such compounds likely is four. These comparisons also show that loss of solvating water from a 4-coordinate vanadate on binding cannot provide a rationale for the spectra of the enzymic complexes. Other comparisons show that neither the binding of metal ions nor protonation nor the binding of vanadate at a site with an unusually high or an unusually low dielectric constant can provide such a rationale. Further comparisons with vanadates known to be pentacoordinate strongly suggest that the coordination number of V(V) in the transition-state-analogue complexes of phosphoglucomutase does not exceed four. In fact, from the standpoint of crystal field theory the marked red shift observed in the electron-transfer absorbance spectrum of the oxyvanadium constellation in these complexes is more reasonably interpreted in terms of a decreased coordination at vanadium (V), viz., in terms of a weakened bonding between vanadium and one or more of its coordinating oxygens. This decreased coordination could be produced by a physical stretching of the vanadate ester linkage. By contrast, the near ultraviolet spectrum of the transition-state-analogue complex that ribonuclease forms with an adduct of uridine and vanadate [Lindquist, R. N., Lynn, J. L., & Lienhard, G. E. (1973) J. Am. Chem. Soc. 95, 8762] is similar to spectra of pentacoordinate model compounds of vanadium(V).(ABSTRACT TRUNCATED AT 400 WORDS)     

The permeability and cytotoxicity of insulin-mimetic vanadium (III,IV,V)-dipicolinate complexes

Vanadium (III,IV,V)-dipicolinate complexes with different redox properties were selected to investigate the structure-property relationship of insulin-mimetic vanadium complexes for membrane permeability and gastrointestinal (GI) stress-related toxicity using the Caco-2 cell monolayer model. The cytotoxicity of the vanadium complexes was assayed with 3-(4,5-dimethylthiazoyl-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assays and the effect on monolayer integrity was measured by the trans-epithelial electric resistance (TEER). The three vanadium complexes exhibited intermediate membrane permeability (P(app) = 1.4-3.6x10(-6) cm/s) with low cellular accumulation level (<1%). The permeability of all compounds was independent of the concentration of vanadium complexes and excess picolinate ligands. Both V(III) and V(V)-dipicolinate complexes induced 3-4-fold greater reactive oxygen and nitrogen species (RONS) production than the V(IV)-dipicolinate complex; while the vanadium (III)-dipicolinate was 3-fold less damaging to tight junction of the Caco-2 cell monolayer. Despite the differences in apparent permeability, cellular accumulation, and capacity to induce reactive oxygen and nitrogen species (RONS) levels, the three vanadium complexes exhibited similar cytotoxicity (IC50 = 1.7-1.9 mM). An ion pair reagent, tetrabutylammonium, increased the membrane apparent permeability by 4-fold for vanadium (III and IV)-dipicolinate complexes and 16-fold for vanadium (V)-dipicolinate as measured by decrease in TEER values. In addition, the ion pair reagent prevented damage to monolayer integrity. The three vanadium (III,IV,V)-dipicolinate complexes may pass through caco-2 monolayer via a passive diffusion mechanism. Our results suggest that formation of ion pairs may influence compound permeation and significantly reduce the required dose, and hence the GI toxicity of vanadium-dipicolinate complexes.     

天然Fe(Ⅱ)矿物-生物质强化微生物还原固定五价钒研究

【目的】重金属钒的环境危害日益受到关注,微生物可实现高毒性的五价钒[pentavalent vanadium, V(Ⅴ)]的还原固定,其中电子供体是微生物还原V(Ⅴ)的关键,尽管天然Fe(Ⅱ)矿物和天然生物质均被报道可单独支持微生物还原V(Ⅴ),而基于两者构建的混养体系中微生物还原V(Ⅴ)的特征尚未揭示。【方法】本研究对天然Fe(Ⅱ)矿物和生物质进行优选并复配组合,探究混养生物体系中五价钒[V(Ⅴ)]的还原机理。【结果】磁黄铁矿和木屑对V(Ⅴ)的去除效率最高,分别为54.2%±3.4%和67.1%±3.1%。当优选的磁黄铁矿与木屑组合复配比例为1:3时可达到最高的V(Ⅴ)去除效率82.7%±3.1%。V(Ⅴ)被还原为不溶性V(Ⅳ)沉淀,Fe(Ⅱ)和S(–Ⅱ)分别被氧化为Fe(Ⅲ)和SO₄^2-。在混养体系中,脱硫菌(Desulfurivibrio)和硫菌属(Thiobacillus)等自养菌属可能参与磁黄铁矿的氧化与V(Ⅴ)还原,并利用无机碳源合成有机中间代谢产物,与无胆甾原体属(Acholeplasma)等纤维素降解菌分解木屑的产物一起,被B...     

Vanadium in Biosphere and Its Role in Biological Processes

Ultra-trace elements or occasionally beneficial elements (OBE) are the new categories of minerals including vanadium (V). The importance of V is attributed due to its multifaceted biological roles, i.e., glucose and lipid metabolism as an insulin-mimetic, antilipemic and a potent stress alleviating agent in diabetes when vanadium is administered at lower doses. It competes with iron for transferrin (binding site for transportation) and with lactoferrin as it is secreted in milk also. The intracellular enzyme protein tyrosine phosphatase, causing the dephosphorylation at beta subunit of the insulin receptor, is inhibited by vanadium, thus facilitating the uptake of glucose inside the cell but only in the presence of insulin. Vanadium could be useful as a potential immune-stimulating agent and also as an antiinflammatory therapeutic metallodrug targeting various diseases. Physiological state and dose of vanadium compounds hold importance in causing toxicity also. Research has been carried out mostly on laboratory animals but evidence for vanadium importance as a therapeutic agent are available in humans and large animals also. This review examines the potential biochemical and molecular role, possible kinetics and distribution, essentiality, immunity, and toxicity-related study of vanadium in a biological system.     

Chemistry and insulin-like properties of vanadium(IV) and vanadium(V) compounds

The chemistry of vanadium compounds that can be taken orally is very timely since a vanadium(IV) compound, KP-102, is currently in clinical trials in humans, and the fact that human studies with inorganic salts have recently been reported. VO(acac)2 and VO(Et-acac)2 (where acac is acetylacetonato and Et-acac is 3-ethyl-2,4-pentanedionato) have long-term in vivo insulin mimetic effects in streptozotocin induced diabetic Wistar rats. Structural characterization of VO(acac)2 and two derivatives, VO(Me-acac)2 and VO(Et-acac)2, in the solid state and solution have begun to delineate the size limits of the insulin-like active species. Oral ammonium dipicolinatooxovanadium(V) is a clinically useful hypoglycemic agent in cats with naturally occurring diabetes mellitus. This compound is particularly interesting since it represents the first time that a well-characterized organic vanadium compound with the vanadium in oxidation state five has been found to be an orally effective hypoglycemic agent in animals.     

Anti-diabetic effects of sodium 4-amino-2,6-dipicolinatodioxovanadium(V) dihydrate in streptozotocin-induced diabetic rats

The evaluation of the anti-diabetic effects of an organic vanadium(V) complex in streptozotocin (STZ)-induced diabetic rats was investigated. The STZ-induced diabetic rats were orally administrated with sodium 4-amino-2,6-dipicolinatodioxovanadium(V) dihydrate (V5dipic-NH₂), a vanadium(V) coordination compound. The compound was administered through drinking water at a concentration of 0.1 mg/mL for 20 days, and then the concentration was increased to 0.3 mg/mL for the following 20 days. At the end of the experiment, V5dipic-NH₂ statistically significantly reduced the levels of blood glucose (P < 0.01), serum total cholesterol (P < 0.01), triglycerides (P < 0.01) and the activities of serum aspartate amino transferase (P < 0.05) and alkaline phosphatase (P < 0.01) compared to untreated diabetic animals. After treatment with 0.3 mg/mL V5dipic-NH₂, the oral glucose tolerance was improved in diabetic animals (P < 0.01). In addition, the daily intake of elemental vanadium was markedly decreased in V5dipic-NH₂-treated diabetic rats compared to vanadyl sulfate (VOSO₄)-treated diabetic rats, which suggested that the anti-diabetic activity of the element vanadium was elevated after being modified with an organic ligand. These results suggested that V5dipic-NH₂, as an organic vanadium compound, is more effective than inorganic vanadium salt at alleviating the symptoms of diabetes.     

Methods for improving the visualization and deconvolution of isotopic signals

Stable isotopes and their associated mechanistic frameworks have provided the means to model biological transformations from inorganic sources to organic sinks, and their impact on long-term terrestrial carbon reservoirs. However, stable isotopes have also the potential to diagnose the mechanisms by which biological systems operate, when using 'multidimensional' analyses of the isotopic outputs. For this purpose, we suggest that isotopic signals may be treated as mathematical vectors to reveal their interrelationships. These visualizations may be achieved, thanks to multidimensional representations (the 'isotopology' method), or by appreciating the colinearity of isotopic vectors to develop a clustering analysis (the 'isotopomic' method) similar to that used in molecular biology. Both methods converge to the same mathematical form, i.e. both lead to a covariation approach. Using simple practical examples, we argue that such procedures allow the deconvolution of plant biological systems by revealing the hierarchy of contributory physiological processes.     

Reduction of vanadium(V) to vanadium(IV) by NADPH, and vanadium(IV) to vanadium(III) by cysteine methyl ester in the presence of biologically relevant ligands

To better understand the mechanism of vanadium reduction in ascidians, we examined the reduction of vanadium(V) to vanadium(IV) by NADPH and the reduction of vanadium(IV) to vanadium(III) by L-cysteine methyl ester (CysME). UV-vis and electron paramagnetic resonance spectroscopic studies indicated that in the presence of several biologically relevant ligands vanadium(V) and vanadium(IV) were reduced by NADPH and CysME, respectively. Specifically, NADPH directly reduced vanadium(V) to vanadium(IV) with the assistance of ligands that have a formation constant with vanadium(IV) of greater than 7. Also, glycylhistidine and glycylaspartic acid were found to assist the reduction of vanadium(IV) to vanadium(III) by CysME.     

Vanadium respiration by Geobacter metallireducens: novel strategy for in situ removal of vanadium from groundwater

Vanadium can be an important contaminant in groundwaters impacted by mining activities. In order to determine if microorganisms of the Geobacteraceae, the predominant dissimilatory metal reducers in many subsurface environments, were capable of reducing vanadium(V), Geobacter metallireducens was inoculated into a medium in which acetate was the electron donor and vanadium(V) was the sole electron acceptor. Reduction of vanadium(V) resulted in the production of vanadium(IV), which subsequently precipitated. Reduction of vanadium(V) was associated with cell growth with a generation time of 15 h. No vanadium(V) was reduced and no precipitate was formed in heat-killed or abiotic controls. Acetate was the most effective of all the electron donors evaluated. When acetate was injected into the subsurface to enhance the growth and activity of Geobacteraceae in an aquifer contaminated with uranium and vanadium, vanadium was removed from the groundwater even more effectively than uranium. These studies demonstrate that G. metallireducens can grow via vanadium(V) respiration and that stimulating the activity of Geobacteraceae, and hence vanadium(V) reduction, can be an effective strategy for in situ immobilization of vanadium in contaminated subsurface environments.     

Bacterial biodegradation of aliphatic sulfides under aerobic carbon- or sulfur-limited growth conditions

AIMS: To isolate bacteria capable of cleaving aliphatic carbon-sulfur bonds as potential biological upgrading catalysts for the reduction of molecular weight and viscosity in heavy crude oil. METHODS AND RESULTS: Thirty-one bacterial strains isolated from enrichment cultures were able to biotransform model compounds representing the aliphatic sulfide bridges found in asphaltenes. Using gas chromatography and mass spectrometry, three types of attack were identified: alkyl chain degradation, allowing use as a carbon source; nonspecific sulfur oxidation; and sulfur-specific oxidation and carbon-sulfur bond cleavage, allowing use as a sulfur source. Di-n-octyl sulfide degradation produced octylthio- and octylsulfonyl-alkanoic acids, consistent with terminal oxidation followed by beta-oxidation reactions. Utilization of dibenzyl sulfide or 1,4-dithiane as a sulfur source was regulated by sulfate, indicating a sulfur-specific activity rather than nonspecific oxidation. Finally, several isolates were also able to use dibenzothiophene as a sulfur source, and this was the preferred organic sulfur substrate for one isolate. CONCLUSIONS: The use of commercially available alkyl sulfides in enrichment cultures gave isolates that followed a range of metabolic pathways, not just sulfur-specific attack. SIGNIFICANCE AND IMPACT OF THE STUDY: These results give new insight into biodegradation of organosulfur compounds from petroleum and for biotreatment of such compounds in chemical munitions.     

Molecular Simulation and the Aggregation of the Heavy Fractions in Crude Oils

The use of Molecular Simulation in the study of aggregates of the molecules of the heavy fractions of crude oils is reviewed. Molecular Mechanics calculations of aggregates of asphaltenes having a single large aromatic region (continental type) and others having smaller aromatic regions connected by alkyl chains (archipelago type) are discussed in terms of the molecular recognition processes present in petroleum. Stacking of the aromatic regions was the most important process in the formation of aggregates of asphaltenes of the continental type with some unfavorable contributions from its saturated rings and alkyl side chains. The steric interference of these groups limits the growth of the aggregates to a small number of molecules. The asphaltenes of the archipelago type showed more complex aggregates because some molecules act as bridges and tangling between them may occur. The interaction of the asphaltene aggregates with resin molecules was analyzed and it was found that the high selectivity for some sites of the asphaltenes explains the specificity of the resins for its own crude oil.     

Do vanadate polyanions inhibit phosphotransferase enzymes?

Decavanadate inhibits hexokinase, adenylate kinase and phosphofructokinase; neither mono-, tri nor tetrameric vanadate anion is an inhibitor. Decavanadate inhibits phosphofructokinase obtained from bacterial and protistic sources. No form of vanadium(V) anion inhibits galacto-, glycero-, pyruvate and creatine kinase, or inorganic pyrophosphatase. Decavanadate appears to be a non-competitive inhibitor of both hexokinase substrates.     

Efficient Perovskite Solar Cells Based on a Solution Processable Nickel(II) Phthalocyanine and Vanadium Oxide Integrated Hole Transport Layer

An organic–inorganic integrated hole transport layer (HTL) composed of the solution‐processable nickel phthalocyanine (NiPc) abbreviated NiPc‐(OBu)₈ and vanadium(V) oxide (V₂O₅) is successfully incorporated into structured mesoporous perovskite solar cells (PSCs). The optimized PSCs show the highest stabilized power conversion efficiency of up to 16.8% and good stability under dark ambient conditions. These results highlight the potential application of organic–inorganic integrated HTLs in PSCs.     

Removal of vanadium from vanadium-containing wastewater by amino modified municipal sludge derived ceramic

In this work, an amino modified porous ceramic derived from municipal sludge was synthesized for the adsorption of vanadium (V) from wastewater. In this approach, a maximum vanadium (V) removal of 99.8% can be achieved by using 800 g adsorbent with a height of 800 mm when the initial concentration of vanadium (V) was 50 mg/L, pH was 4, flow rate was 5 L/h.