Titanium Citrate Research Articles

Real-time monitoring of Ti(IV) metal ion binding of transferrin using a solid-state nanopore.

Transferrin, a central player in iron transport, has been recognized not only for its role in binding iron but also for its interaction with other metals, including titanium. This study employs solid-state nanopores to investigate the binding of titanium ions [Ti(IV)] to transferrin in a single-molecule and label-free manner. We demonstrate the novel application of solid-state nanopores for single-molecule discrimination between apo-transferrin (metal-free) and Ti(IV)-transferrin. Despite their similar sizes, Ti(IV)-transferrin exhibits a reduced current drop, attributed to differences in translocation times and filter characteristics. Single-molecule analysis reveals Ti(IV)-transferrin's enhanced stability and faster translocations due to its distinct conformational flexibility compared to apo-transferrin. Furthermore, our study showcases solid-state nanopores as real-time monitors of biochemical reactions, tracking the gradual conversion of apo-transferrin to Ti(IV)-transferrin upon the addition of titanium citrate. This work offers insights into Ti(IV) binding to transferrin, promising applications for single-molecule analysis and expanding our comprehension of metal-protein interactions at the molecular level.

Menaquinone Biosynthesis: The Mechanism of 5,8-Dihydroxy-2-naphthoate Synthase (MqnD).

MqnD catalyzes the conversion of cyclic dehypoxanthine futalosine (6) to 5,8-dihydroxy-2-naphthoic acid (7) and an uncharacterized product. This study describes a chemoenzymatic synthesis of 6. This synthesis achieved a 2-fold yield enhancement by using titanium(III) citrate as the reducing agent and another 5-fold yield enhancement using a fluorinated analogue of dehypoxanthine futalosine (5) that was converted to 6 by an ipso substitution mechanism. This synthetic route enabled the synthesis of 6 in sufficient quantity to identify the second reaction product and to determine that the MqnD-catalyzed reaction proceeds by a hemiacetal ring opening-tautomerization-retroaldol sequence.

Fabrication of highly ordered mesoporous titania via micelle fusion-aggregation assembly route by synergistic interactions among titanium precursor, block copolymer templates and solvent

Mesoporous titania has gained increasing interest because of its outstanding properties and promising applications in a wide range of fields. Herein, highly ordered mesoporous titania with a hexagonal mesostructure has successfully been synthesized via the solvent evaporation induced micelle fusion–aggregation assembly method by using polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) diblock copolymer as a template, titanium citrate (TIC) as a precursor and a mixture of pyridine and ethanol as the solvent. It is worth noting that addition of pyridine to the system can generate the synergistic interactions among titanium precursor, block copolymer templates and solvent and give the PS-b-P2VP/TIC composite micelles enough time to assemble into the ordered structures during the evaporation-induced self-assembly (EISA) process. The prepared highly ordered mesoporous TiO2 samples were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), small angle X-ray scattering (SAXS), UV–vis diffuse reflectance spectrophotometry and N2 adsorption analysis etc. By using the highly ordered mesoporous titania as photocatalysts in degradation of methylene blue (MB) under visible light irradiation, a high photocatalytic performance can be achieved and enhanced via further doping, which show that the highly ordered mesoporous titania have a potential application in wastewater treatment.

Abiotic reductive deiodination of iodinated organic compounds and X-ray contrast media catalyzed by free corrinoids

Iodinated X-ray contrast media are known for their stability concerning deiodination in the aquatic environment under aerobic conditions. In this study, we demonstrate the abiotic reductive deiodination of the iodinated contrast media iopromide, iopamidol and diatrizoate in the presence of corrinoids. In addition, triiodinated benzoic acid derivatives with iodine atoms bound at different positions were investigated. Corrinoids like cyanocobalamin (vitamin B12) and dicyanocobinamide served as electron shuttles and as catalysts between the reducing agent (e.g., titanium (III) citrate) and the electron accepting iodinated compound. The concentration decrease of the iodinated compounds followed first-order kinetics with rate constant kobs depending on the iodinated compound. A linear correlation between the rate of iodide release and the corrinoid concentration was observed, with deiodination rates for dicyanocobinamide twice as high as for vitamin B12. Reducing agents with a less negative standard redox potential like dithiothreitol or cysteine caused slower deiodination as the cobalt center was only reduced to its CoII oxidation state. With a temperature increase from 11 to 23 °C, the concentrations of released iodide doubled. A complete deiodination was only observed for the iodinated contrast media but not for structurally similar iodinated benzoic acid derivatives.

Distinct Carbon Isotope Fractionation Signatures during Biotic and Abiotic Reductive Transformation of Chlordecone.

Chlordecone is a synthetic organochlorine pesticide, extensively used in banana plantations of the French West Indies from 1972 to 1993. Due to its environmental persistence and bioaccumulation, it has dramatic public health and socio-economic impact. Here we describe a method for carbon-directed compound specific isotope analysis (CSIA) for chlordecone and apply it to monitor biotic and abiotic reductive transformation reactions, selected on the basis of their distinct product profiles (polychloroindenes versus lower chlorinated hydrochlordecones). Significant carbon isotopic enrichments were observed for all microbially mediated transformations (εbulk = -6.8‰ with a Citrobacter strain and εbulk = -4.6‰ with a bacterial consortium) and for two abiotic transformations (εbulk = -4.1‰ with zerovalent iron and εbulk = -2.6‰ with sodium sulfide and vitamin B12). The reaction with titanium(III) citrate and vitamin B12, which shows the product profile most similar to that observed in biotic transformation, led to low carbon isotope enrichment (εbulk =-0.8‰). The CSIA protocol was also applied on representative chlordecone formulations previously used in the French West Indies, giving similar chlordecone δ13C values from -31.1 ± 0.2‰ to -34.2 ± 0.2‰ for all studied samples. This allows the in situ application of CSIA for the assessment of chlordecone persistence.

Reductive defluorination of perfluorooctanoic acid by titanium(III) citrate with vitamin B12 and copper nanoparticles

Perfluorooctanoic acid (PFOA) is widespread in the environment, which causes serious health and safety concerns. A mechanistic study on reductive defluorination of PFOA by titanium(III) citrate in the presence of catalysts was conducted. Vitamin B12 was used to catalyze reduction reactions by shuttling electrons from a reducing agent (electron donor) to PFOA to produce a Co-carbon bond intermediates. In the presence of copper nanoparticles, a precursor complex, B12-C7F14COOH, adsorbed on the metal surface, followed by a hydrogenolytic reaction to form less-fluorinated products. The synergistic effect between vitamin B12 and copper nanoparticles enhances the reductive activities by electron-transfer reactions and hydrogenolysis. The efficient reduction of PFOA to less-noxious compounds was demonstrated with a copper dose of 2gL−1, titanium(III) citrate (45mM), and vitamin B12 (0.2mM) with an initial pH of 9.0 and 70°C. In this anoxic aqueous solution, the biomimetic reductive system effectively removed 65% of PFOA. The mass balance on fluoride matched the observed degradation of PFOA, while no short-chain intermediates were detected.

Mechanistic aspects of photocatalytic activity of metalloporphyrin–titanium mixtures in microemulsions

Photocatalytic activity of titanium citrate and its water-in-oil microemulsions mix with zinc (II) tetraphenylporphyrin have been studied by means of adding 4-chlorophenol and following its degradation using artificial ultraviolet and visible light. 4-Chlorophenol is degraded in 71 and 86%, respectively, in 30 min with the generation of various intermediaries, whose possible formation mechanisms have been proposed based in the results of this research. The generation of benzene derivatives, different to those usually reported for this type of treatment, suggests the possibility of controlling the generation of intermediaries by simply changing the type of surfactant. In the case discussed here, we have derived a simple method for isomer generation of trimethylbenzene using a model organohalogenated compound as water contaminant and cetyltrimethylammonium bromide as surfactant.

Effect of different starting materials on the synthesis of Ba0.8Ca0.2TiO3

Literature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction, co-precipitation and polymer precursors. These compounds are usually obtained using calcium carbonate (CaCO3), barium carbonate (BaCO3) and titanium oxide as starting materials. This study investigated the effect of different starting reagents on the synthesis of Ba0.8Ca0.2TiO3 (BCT) by complex polymerization method (CPM). Two sets of starting precursors were used: titanium citrate, CaCO3 and BaCO3, and titanium citrate and Ba1−x Ca x CO3 solid solution precursor. Samples were crystallized at a temperature range from 400 °C to 700 °C for different time. The obtained powders were characterized by X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), and Raman and infrared spectroscopy. The infrared spectroscopy indicated that the chelation processes of Ba, Ca, Ti and CA ions are very similar. The results showed that the use of CaCO3 and BaCO3 or Ba1−x Ca x CO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPM.

One-Step Hydrothermal-Electrochemical Route to Carbon-Stabilized γ-Fe2O3 Powders

Black carbon-stabilized anatase particles were prepared by a simple one-step hydrothermal–electrochemical method using glucose and titanium citrate as the carbon and titanium source, respectively. Morphological, chemical, structural, and electrochemical characterizations of these powders were carried out by Raman spectroscopy, Fourier-transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and cyclic voltammetry. It was revealed that 200-nm carbon/anatase TiO2 was homogeneously dispersed, and the powders exhibited excellent cyclic performance at high current rates of 0.05 V/s. The powders are interesting potential materials that could be used as anodes for lithium-ion batteries.

Spectroscopic characterization and mechanistic investigation of P-methyl transfer by a radical SAM enzyme from the marine bacterium Shewanella denitrificans OS217

Natural products containing carbon–phosphorus bonds elicit important bioactivity in many organisms. l-Phosphinothricin contains the only known naturally-occurring carbon–phosphorus–carbon bond linkage. In actinomycetes, the cobalamin-dependent radical S-adenosyl-l-methionine (SAM) methyltransferase PhpK catalyzes the formation of the second C–P bond to generate the complete C–P–C linkage in phosphinothricin. Here we use electron paramagnetic resonance and nuclear magnetic resonance spectroscopies to characterize and demonstrate the activity of a cobalamin-dependent radical SAM methyltransferase denoted SD_1168 from Shewanella denitrificans OS217, a marine bacterium that has not been reported to synthesize phosphinothricin. Recombinant, refolded, and reconstituted SD_1168 binds a four-iron, four-sulfur cluster that interacts with SAM and cobalamin. In the presence of SAM, a reductant, and methylcobalamin, SD_1168 surprisingly catalyzes the P-methylation of N-acetyl-demethylphosphinothricin and demethylphosphinothricin to produce N-acetyl-phosphinothricin and phosphinothricin, respectively. In addition, this enzyme is active in the absence of methylcobalamin if the strong reductant titanium (III) citrate and hydroxocobalamin are provided. When incubated with [methyl-13C] cobalamin and titanium citrate, both [methyl-13C] and unlabeled N-acetylphosphinothricin are produced. Our results suggest that SD_1168 catalyzes P-methylation using radical SAM-dependent chemistry with cobalamin as a coenzyme. In light of recent genomic information, the discovery of this P-methyltransferase suggests that S. denitrificans produces a phosphinate natural product.

Plants of Constructed Wetland Wastewater Treatment Systems: A Comparison of the Oxygen Release from Roots of Typha and Phragmite

Constructed wetlands have recently been widely used around the world to purify wastewater. As an important component of constructed wetland system, plants improve water quality by increasing oxygen concentrations in the rhizosphere. However, little was known about the ability of oxygen release from roots with different species. And the reason of the difference is still unclear. This paper investigated the variation of oxygen release rate from roots ofTyphaandphragmiteusing a titanium (Ш) citrate buffer. Compared the ability of oxygen release fromTyphaandphragmite. The results shows that oxygen release rates with the same condition were higher forPhragmites. This difference is caused by the special structure ofPhragmites. The aerenchyma ofPhragmitesis good at the oxygen transport. The results of this paper can help us to choose better vegetation species for wastewater treatment.

Sol-gel synthesis of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

A modified sol-gel process was studied as applied to synthesize a lithium-conducting solid electrolyte of composition Li1.3Al0.3Ti1.7(PO4)3 (LATP) using water-soluble salts Al(NO3)3 · 9H2O, LiNO3 · 3H2O, and (NH4)2HPO4 and a titanium(IV) citrate complex. As-synthesized samples were characterized using X-ray powder diffraction, DSC/TG, SEM, and impedance spectroscopy. Sintering of as-synthesized amorphous powders at 700°C was found to yield LATP with crystallite sizes of 42–48 nm. Ionic conductivity of the electrolyte measured in the frequency range 25–106 Hz in disks having 86–90% density that were sintered at 1000°C was (3–4) × 10−4 S/cm. Temperature-dependent ionic conductivity was studied in the range 25–200°C. The activation energy of conduction was determined for LATP.

Increased Ginsenosides Production by Elicitation of In vitro Cultivated Panax Ginseng Adventitious Roots

Ginsenosides, which belong to group of triterpenoid saponins, are considered to be main constituents responsible for the biological effects of ginseng drug. Effect of organic and inorganic elicitors and other additives on the ginsenoside biosynthesis and biomass production by the in vitro cultivated adventitious root cultures of Korean ginseng was investigated in present study. Elicitation potential of natural mixtures (coconut water, pineapple extract, casein hydrolyzate, yeast extract, malt extract), organic elicitors (putrescine, spermidine, spermine, jasmonic acid), inorganic ions (calcium) and their complexes with organic acids (titanium ascorbate, titanium citrate) was tested. Changes in concentration of 9 main ginsenosides (Re, Rg1 , Rf, Rg2 , Rb1 , Rb2 , Rc, Rg3 and Rd) were monitored using HPLC-PDA and LC/MS/MS techniques. Jasmonic acid was the most effective elicitor of ginsenoside production (about 3.5 mg/g of DW in comparison with 1.4 mg/g of DW in control); however, its application (similar to spermine) was followed with significant reduction of the biomass growth. Among tested additives, casein hydrolyzate showed the highest increase of the ginsenoside content (2.2 mg/g DW) together with no effect on the growth of the culture. Both tested titanium complexes showed slight inhibition of the saponin accumulation in comparison with untreated control.

One-Step Hydrothermal–Electrochemical Route to Carbon-Stabilized Anatase Powders

Black carbon-stabilized anatase particles were prepared by a simple one-step hydrothermal–electrochemical method using glucose and titanium citrate as the carbon and titanium source, respectively. Morphological, chemical, structural, and electrochemical characterizations of these powders were carried out by Raman spectroscopy, Fourier-transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and cyclic voltammetry. It was revealed that 200-nm carbon/anatase TiO2 was homogeneously dispersed, and the powders exhibited excellent cyclic performance at high current rates of 0.05 V/s. The powders are interesting potential materials that could be used as anodes for lithium-ion batteries.

Synergistic effect of zero-valent copper nanoparticles on dichloromethane degradation by vitamin B12 under reducing condition

While zero-valent iron (ZVI, an electron donor) can degrade many kinds of chlorinated organic contaminants and vitamin B12 (an electron mediator) is capable of enhancing the degradation, both are ineffective in degrading dichloromethane (DCM). In this study, we found that a combination of zero-valent copper (Cu0) nanoparticles and vitamin B12 can catalyze the degradation of DCM effectively under reducing conditions when titanium citrate was used as the reducing agent. Batch experiments were performed to test the effectiveness of the Cu0–B12 system in DCM degradation. Approximately 99% of 26mg/L DCM was degraded rapidly within 2h by the Cu0–B12 system. The observed pseudo-first-order rate constant was 1.35h−1, which was five times greater than that of using vitamin B12 alone. A synergistic effect of Cu0 nanoparticles on the reductive degradation of DCM by vitamin B12 was found. Soluble copper ions generated by the dissolution of Cu0 nanoparticles were lower than the WHO-specified limit for drinking water. It is expected that the combination of Cu0 nanoparticles and electron mediator system may have the potential for treating recalcitrant groundwater contaminants that cannot be degraded by ZVI technology.

Titanium mineralization in ferritin: a room temperature nonphotochemical preparation and biophysical characterization

The incremental addition of titanium(III) citrate to H-chain homopolymers of human ferritin results in the formation of 1.5-6.5-nm particles of amorphous TiO(2) within the nanocage of the protein. The mineralization conditions are mild, featuring ambient temperature and no need for photochemical activation. Low ratios of titanium to protein favor intraprotein mineralization, and the products are characterized by stained and unstained transmission electron microscopy, UV-vis spectroscopy, dynamic light scattering, analytical ultracentrifugation, and metal analysis. With up to 1,000 equiv of metal, there is no change to the protein hydrodynamic radius or diffusion constant. There is, however, a systematic shift in the sedimentation coefficient, which confirms mineralization within the protein core.

Ordered mesoporous carbide-derived carbons prepared by soft templating

Free-standing films of ordered mesoporous silicon and titanium carbide-derived carbons have been synthesized using a novel soft templating approach without employing hydrofluoric acid. Tetraethyl orthosilicate or titanium citrate, alternatively, and a phenolic resin underwent an evaporation induced self-assembly yielding ordered mesoporous silicon carbide/carbon or titanium carbide/carbon composites. High temperature chlorine treatment transformed these materials conformally into carbide-derived carbons (CDC) while the ordered arrangement of mesopores was maintained. The corresponding hierarchical pore structures consist of narrowly distributed micro- and mesopores (distribution maxima at 1 and 5nm, respectively) with a high surface area and pore volume of up to 1538m2/g and 2.53cm3/g, respectively.

Isolation and characterization of tetrachloroethylene- and cis-1,2-dichloroethylene-dechlorinating propionibacteria

Two rapidly growing propionibacteria that could reductively dechlorinate tetrachloroethylene (PCE) and cis-1,2-dichloroethylene (cis-DCE) to ethylene were isolated from environmental sediments. Metabolic characterization and partial sequence analysis of their 16S rRNA genes showed that the new isolates, designated as strains Propionibacterium sp. HK-1 and Propionibacterium sp. HK-3, did not match any known PCE- or cis-DCE-degrading bacteria. Both strains dechlorinated relatively high concentrations of PCE (0.3 mM) and cis-DCE (0.52 mM) under anaerobic conditions without accumulating toxic intermediates during incubation. Cell-free extracts of both strains catalyzed PCE and cis-DCE dechlorination; degradation was accelerated by the addition of various electron donors. PCE dehalogenase from strain HK-1 was mediated by a corrinoid protein, since the dehalogenase was inactivated by propyl iodide only after reduction by titanium citrate. The amounts of chloride ions (0.094 and 0.103 mM) released after PCE (0.026 mM) and cis-DCE (0.05 mM) dehalogenation using the cell-free enzyme extracts of both strains, HK-1 and HK-3, were stoichiometrically similar (91 and 100%), indicating that PCE and cis-DCE were fully dechlorinated. Radiotracer studies with [1,2-¹⁴C] PCE and [1,2-¹⁴C] cis-DCE indicated that ethylene was the terminal product; partial conversion to ethylene was observed. Various chlorinated aliphatic compounds (PCE, trichloroethylene, cis-DCE, trans-1,2-dichloroethylene, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, and vinyl chloride) were degraded by cell-free extracts of strain HK-1.

Diurnal fluctuations in oxygen release from roots of Acorus calamus Linn in a modeled constructed wetland

Oxygen is known to be released from plant roots, but has seldom been quantified for wetland plants. Our study aims to quantify oxygen release from the roots of one wetland species in China, and use this knowledge as a basis for future modeling. We measured diurnal fluctuations in oxygen release from the roots of Acorus calamus Linn in a modeled constructed wetland (CW) using a titanium () citrate buffer. Oxygen release was monitored every two hours. Maximum oxygen release was recorded in the range of 215.2–750.8 μmolg−1h−1 and occurred around 15:00. The maximum value of photosynthetically active radiation (PAR) was in the range of 1281.8–1712.0 mmolm−2s−1 and occurred around 13:00. Both the oxygen release rate and PAR were found to approach zero at night. Our results indicate that oxygen release depends largely on light intensity and exhibits a diurnal periodicity with release occurring only during daytime. Rate of root oxygen release varied during the daytime and this temporal variation was well described by the Gaussian function. While further validation is needed, we suggest that the Gaussian function may be used as the basis for modeling root oxygen release in natural and constructed wetlands.

Morphological and Functional Alterations in Human Red Blood Cells Treated with Titanium Citrate

The morphological and functional effects of titanium (Ti) citrate on human erythrocytes were studied by scanning electron microscope (SEM), sulphate uptake via band 3 protein and by determining the reduced and oxidised glutathione (GSH and GSSG, respectively) concentrations. The rate constant for sulphate uptake was significantly lower after Ti citrate treatment. Ti citrate (0.001 and 0.0025 mM) significantly decreased erythrocyte GSH and increased GSSG concentrations. At 0.005 mM Ti citrate, the intracellular GSH could not be tested due to significant cellular damage. SEM of erythrocytes treated with 0.001 mM and 0.0025 mM Ti citrate showed structural membrane defects but almost normal cellular diameters. At even higher Ti citrate concentrations (0.005 mM), erythrocytes showed obvious morphological alteration and shape changes compromising the cells physiological functions. In conclusion, although the Ti concentrations used in our experiments are physiologically high, the cumulative effect of prolonged exposure to much lower doses of Ti, as might occur during total hip replacement, should be considered for further experimental testing.