Use Of Thiourea Research Articles

End-performance evaluation of thiourea-modified bituminous binders through viscous flow and linear viscoelasticy testing

Straight-run bitumens are no longer suitable in new asphalt mixtures. Consequently, the use of modified bitumens has become more important. In order to both improve binders’ mechanical properties and prevent it from phase separation whilst stored at high temperature, the paving industry is currently developing new modification routes based on reactive agents. This work studies the use of thiourea, which has proven to efficiently broaden the temperature interval over which the binder demonstrates an adequate performance. On the one hand, viscous flow and dynamic shear tests indicate an enhancement in the high in-service temperature strength, along with a reduced thermal susceptibility. On the other hand, results of dynamic flexural tests reveal a significant decrease in the binder glass transition temperature. Finally, the use of master curves and a further frequency/temperature conversion are proposed, in order to attain a suitable viscoelastic characterisation of bituminous binders at low temperatures.

Divergent Cyclizations of 1-R-Ethynyl-9,10-anthraquinones: Use of Thiourea as a “S2–” Equivalent in an “Anchor-Relay” Addition Mediated by Formal C–H Activation

The EtONa-mediated reaction of peri-R-ethynyl-9,10-anthraquinones with thiourea yields 2-R-7H-dibenzo[de,h]quinolin-7-ones and 2-R-anthra[2,1-b]thiophene-6,11-diones. Although 2-R-7H-dibenzo[de,h]quinolin-7-ones were observed previously in reactions with other N-centered nucleophiles (hydrazine, guanidine, and urea), the formation of 2-R-anthra[2,1-b]thiophene-6,11-diones is a new reactivity path. DFT computations analyzed factors responsible for the switch in reactivity and the relative importance of two possible pathways: (1) the "anchor-relay" mechanism mediated by nucleophilic attack at the carbonyl and (2) direct attack at the alkyne. The two pathways converge on a vinyl sulfur anion, set up for a 5-endo-trig cyclization at the ortho-position. Subsequent rearomatization/oxidation provides the fused thiophene product via formal C-H activation. The calculations suggest that the latter pathway, the direct attack at the alkyne, is more likely, due to the relatively high barrier for the 8-endo-dig cyclization (pathway 1). Computational insights led to a more selective synthesis of fused thiophenes, based on the reaction of acetylenic anthraquinones with sodium sulfide. This reaction does not require prefunctionalization at the ortho-position since direct C-H activation is efficient. The absence of fused five-membered heterocycles in earlier work was investigated computationally. The other N-centered nucleophiles form stronger anion-π complexes with the electron-deficient quinone core, promoting carbonyl attack over direct alkyne attack.

Enhancing the viscoelastic properties of bituminous binders via thiourea-modification

Although added in a very low concentration, bitumen controls the final properties and performance of the resulting asphalt mixture. As an alternative to classic bitumen modification with polymers, we herein propose the use of thiourea, which has proved to efficiently enhance the binder thermo-rheological properties in a broad temperature interval. As revealed by thermogravimetric and chemical analysis, benefits above may derive from new structures, probably formed by the interaction between ammonium thiocyanate and bitumen most polar fraction. Thus, flexural DMTA and dynamic shear tests demonstrated an improvement in the binder flexibility and an increase in its elasticity, at low and medium/high in-service temperatures, respectively. In addition, this research emphasizes the use of isothermal frequency sweep tests (and frequency/temperature-dependence conversion) as a means of achieving glass transition temperature values which, in contrast to isochronal temperature sweep tests, do not depend on the selected heating rate.

Modifying polymer flocculants for the removal of inorganic phosphate from water

Due to strong hydrogen bonding interactions, thiourea has been shown to have a high affinity for anions such as inorganic phosphate. The interaction between phosphate and thiourea has been used to develop technologies that can detect and even remove phosphate from water. This research investigates the use of thiourea derivatized polymer flocculants for the sequestering of inorganic phosphate from water. The study presented herein describes the development of a thiourea based monomer that was used to create a bi-functional polymer that flocculates suspended solid material as well as sorbs phosphate, removing both from water. The new polymer removed more than 60% of the phosphate from a simulated wastewater sample. The addition of a thiourea trapping group to the polymer more than doubled the amount of phosphate removed from solution compared to control polymers.

Genome-wide analysis of thiourea-modulated salinity stress-responsive transcripts in seeds of Brassica juncea: identification of signalling and effector components of stress tolerance

Abiotic stresses including salinity are the major constraints to crop production. In this regard, the use of thiourea (TU) in imparting salinity-stress tolerance to Indian mustard (Brassica juncea) has been demonstrated earlier. To gain an insight into the mechanism of TU action, various molecular and biochemical studies were conducted. Microarray analysis was performed in seeds subjected to distilled water (control), 1 m NaCl, 1 m NaCl + 6·5 mm TU and 6·5 mm TU alone for 1 h. Real-time PCR validation of selected genes and biochemical studies were conducted under similar treatments at 1 h and 6 h. The microarray analysis revealed a differential expression profile of 33 genes in NaCl- and NaCl + TU-treated seeds, most of which are established markers of stress tolerance. The temporal regulation of eight selected genes by real-time PCR indicated their early and co-ordinated induction at 1 h in NaCl + TU only. Besides, NaCl + TU-treated seeds also maintained a higher level of abscisic acid, reduced to oxidized glutathione (GSH : GSSG) ratio and activities of catalase, phenylalanine ammonia lyase and glutathione-S-transferases, as compared with that of NaCl treatment. The addition of LaCl(3) (a specific calcium-channel blocker) restricted the responses of TU both at molecular and biochemical level suggesting the possible involvement of a cytosolic calcium burst in the TU-mediated response. The TU-alone treatment was comparable to that of the control; however, it reduced the expression of some transcription factors and heat-shock proteins presumably due to the stabilization of the corresponding proteins. The TU treatment co-ordinately regulates different signalling and effector mechanisms at an early stage to alleviate stress even under a high degree of salinity. This also indicates the potential of TU to be used as an effective bioregulator to impart salinity tolerance under field conditions.

El camino de la fórmula: el caso del uso de tiourea para limpieza de plata

The use of thiourea for the cleaning of silver cultural heritage has not been absolutely convenient. Apart from having a 0-pH, as a result from the presence of clorhidric acid, which affects the conservation of the constituent materials, the bibliography indicates that its residues cannot be completely eliminated, that it forms secondary by-products, and that it might cause superficial micro-fissures. Hence, this article critics its use, as an example of the application of materials, that by habit –without investigating its consequences, its mechanisms of action, its interactions, and its secondary by-products– have lead to serious mistakes in the intervention. It additionally analyses the profesional attitude that can place restoration as an art-craft: an activity that prioritizes manual skills and the application of formulas over the self-reflection and investigation. It concludes that a scientific thinking is indispensable for the discipline development.

A Simple Method for Synthesis of S-Doped TiO2 of High Photocatalytic Activity

S-doped TiO2 samples were synthesized by use of thiourea. The elemental analysis was confirmed by X-ray fluorescence, the phases were identified by X-ray diffraction and further characterization was carried out by surface area measurement and UV–Vis spectroscopy. The photocatalytic activity was measured by exposing methylene blue to sunlight in the presence of TiO2. It was observed that the S-doped anatase phase showed high photocatalytic activity in comparison to other samples.

Thematic Review Series: Proteomics. Proteomic analysis of lipid-protein complexes

There is intense interest in comprehensive proteomic approaches for analyzing integral membrane proteins and lipoproteins. Key features of mass spectrometric analysis center on enriching biological material for proteins of interest, efficiently digesting them, extracting the resulting peptides, and using fractionation methods to comprehensively sample proteins or peptides by tandem mass spectrometry. However, lipid-associated proteins are generally rich in hydrophobic domains and are often low in abundance. These features, together with the associated lipid, make their mass spectrometric analysis technically challenging. In this article, we review analytical strategies for successful proteomic analysis of lipid-associated proteins.

A general method for the extraction of citrus leaf proteins and separation by 2D electrophoresis: A follow up

With the aim of studying differentially expressed proteins as a function of abiotic and biotic stress in citrus plants, we optimized a protocol for the extraction of total leaf proteins and their 2-DE separation using commercially available immobilized pH gradient strips (IPGs) in the first dimension. Critical factors for good reproducibility of citrus leaf protein separation were identified: trichloroacetic acid (TCA)/acetone precipitation after extraction in lysis buffer, sample fractionation on narrow range overlapping IPGs and sample-cup loading at the anodic or cathodic end of the strip. The use of thiourea and a strong detergent (C7BzO) in the solubilization/rehydration buffer, coupled with the increase to 10% of SDS in the equilibration buffer before the second dimension seemed to affect positively the resolution of basic proteins. Using our protocol we resolved about 30 basic proteins on 6.3–8.3 pH range strips. Further, our protocol was successfully applied reproducibly on the analysis of control and salt exposed leaf samples of Citrus reshni Hort. Ex Tan.

A REVIEW OF GOLD LEACHING IN ACID THIOUREA SOLUTIONS

Since the initial report of thiourea as a complexing reagent for gold leaching, considerable research has been directed toward the use of thiourea as an alternative to cyanide for gold extraction from different auriferous mineral resources. At the same time, some fundamental investigations of the system have been reported. In this article, a review of both applications and fundamental research is made, including a review of the recent results from laboratory studies at the University of Utah. Recent research results demonstrate that thiourea decomposition is quite slow in the presence of ferric sulfate for simple solutions. Ferric sulfate and formamidine disulfide (FDS) are effective oxidants with fast kinetics. No passivation of the gold surface is observed in simple acidic solutions. However, in actual leaching systems, some sulfide minerals significantly catalyze the redox reaction between thiourea and ferric ion, causing high thiourea consumption if ferric ion is present in excess. The presence of copper has a deleterious influence on this leaching system.

Identification of Proteomic Signatures of Exposure to Marine Pollutants in Mussels (Mytilus edulis)

Bivalves and especially mussels are very good indicators of marine and estuarine pollution, and so they have been widely used in biomonitoring programs all around the world. However, traditional single parameter biomarkers face the problem of high sensitivity to biotic and abiotic factors. In our study, digestive gland peroxisome-enriched fractions of Mytilus edulis (L., 1758) were analyzed by DIGE and MS. We identified several proteomic signatures associated with the exposure to several marine pollutants (diallyl phthalate, PBDE-47, and bisphenol-A). Animals collected from North Atlantic Sea were exposed to the contaminants independently under controlled laboratory conditions. One hundred and eleven spots showed a significant increase or decrease in protein abundance in the two-dimensional electrophoresis maps from the groups exposed to pollutants. We obtained a unique protein expression signature of exposure to each of those chemical compounds. Moreover a set of proteins composed a proteomic signature in common to the three independent exposures. It is remarkable that the principal component analysis of these spots showed a discernible separation between groups, and so did the hierarchical clustering into four classes. The 14 proteins identified by MS participate in alpha- and beta-oxidation pathways, xenobiotic and amino acid metabolism, cell signaling, oxyradical metabolism, peroxisomal assembly, respiration, and the cytoskeleton. Our results suggest that proteomic signatures could become a valuable tool to monitor the presence of pollutants in field experiments where a mixture of pollutants is often present. Further studies on the identified proteins could provide crucial information to understand possible mechanisms of toxicity of single xenobiotics or mixtures of them in marine ecosystems.

Dual mode sample introduction for multi-element determination by ICP-MS: the optimization and use of a method based on simultaneous introduction of vapor formed by NaBH4 reaction and aerosol from the nebulizer

A method has been developed utilizing dual mode sample introduction of a commercial Multi Mode Sample Introduction System (MSIS™) for simultaneous multi-element (As, Bi, Cd, Co, Cu, Ni, Pb, Sb, Zn) determination by ICP-MS. Vapor formed by NaBH4 reaction and aerosol from the nebulizer were introduced simultaneously into the plasma. The effects of parameters that are expected to affect hydride generation of As, Bi and Sb, i.e. concentrations of HNO3, NaBH4 and thiourea, plus flow rates of sample and NaBH4, were evaluated using Plankett–Burman experimental design. Then, the most significant of the parameters were optimized using a central composite design. Further, as optimum values were not the same for all the elements, a response optimizer was used to obtain a compromised optimum. Except for Pb, the sensitivity of the ‘classical’ hydride generating elements (As, Bi and Sb) increased significantly using the dual mode sample introduction, compared to pneumatic nebulization. The factors of sensitivity increase for As, Bi and Sb were 77, 33 and 56, respectively. For the other elements (Cd, Co, Cu, Ni and Zn), that are also reported to react with NaBH4 forming volatile species, no significant change in sensitivity was observed. The limits of detection obtained for As, Bi, and Sb using dual mode sample introduction were 7, 15 and 10 pg mL−1, respectively. The use of thiourea as a pre-reducing agent and masking agent was also investigated. The accuracy of the method was verified by analyzing various certified reference materials (CRMs): SRM1572 ‘Citrus leaves’, SRM1575 ‘Pine Needles’, SRM1643e ‘Trace Elements in Water’, GBW07602 ‘Bush Branches and Leaves’ and GBW07601 ‘Human hair’.

Biginelli reaction on 4-oxo-4H-1-benzopyran-3-carboxaldehyde- a search for reaction pathway

On heating a mixture of 3-formylchromone 1, active methylene compound 2 or 3 and urea (4) in AcOH produces dihydropyrimidinones 10 or 11, whereas use of thiourea in place of urea produces 1,3-thiazine derivative 14 or 15 and the above reactions pass through the Knoevenagel condensate 5 or 6.

Sequential fractionation and two-dimensional gel analysis unravels the complexity of the dimorphic fungus Candida albicans cell wall proteome.

The cell wall proteins of Candida albicans play a key role in morphogenesis and pathogenesis and might be potential target sites for new specific antifungal drugs. However, these proteins are difficult to analyze because of their high heterogeneity, interconnections with wall polysaccharides (mannan, glucan, and chitin), low abundance, low solubility, and hydrophobic nature. Here we report a subproteomic approach for the study of the cell wall proteins (CWPs) from C. albicans yeast and hyphal forms. Most of the mannoproteins present in this compartment were extracted by cell wall fractionation according to the type of interactions that they establish with other structural components. CWPs were solubilized from isolated cell walls by hot SDS and dithiothreitol treatment followed by extraction either by mild alkali conditions or by enzymatic treatment with glucanases and chitinases. These highly enriched cell wall fractions were analyzed by two-dimensional PAGE, showing that a large number of proteins are involved in cell wall construction and that the wall remodeling that occurs during germ tube formation is related to changes in the composition of CWPs. We suggest that the CWP-chitin linkage is an important retention mechanism of CWPs in C. albicans mycelial forms. This article also highlights the usefulness of the combination of sequential fractionation and two-dimensional PAGE followed by Western blotting using specific antibodies against known CWPs in the characterization of incorporation mechanisms of such CWPs into the cell wall and of their interactions with other wall components. Mass spectrometry analyses have allowed the identification of several cell surface proteins classically associated with both the cell wall and other compartments. The physiological significance of the dual location of these moonlighting proteins is also discussed. This approach is therefore a powerful tool for obtaining a comprehensive and integrated view of the cell wall proteome.

Gold electrowinning from thiourea solutions

The use of thiourea as an alternative non-polluting reagent for gold leaching is very well known. However, the processes of gold recovering from thiourea solutions have received little attention, particularly the electrowinning process. Gold electrowinning from thiourea solutions was studied by linear sweep voltammetry and chronopotentiometry. For potentials more cathodic than 0 mV vs. SCE gold reduction is mass transport controlled. The estimated diffusion Coefficient for the complex gold (I)-thiourea, at 25°C was 1.0 × 10 −5, cm 2s −1. The influence of gold, thiourea and formamidine disulfide concentrations on the cathodic behavior ofgold is described. A passivation due to thiourea adsorption on the electrode surface was observed at −300mV vs. SCE. Experiments shown that gold reduction is favored by low thiourea and formamidine disulfide concentrations. Chronopotentiometric measurements indicated the presence of an adsorption step before the reduction of the complex gold (I) -thiourea, although the reduction of the species in solution is also feasible. The influence of current density on the cathodic current efficiency and gold structure is presented.

Electrowinning of zinc

The use of thiourea as an alternative non-polluting reagent for gold leaching is very well known. However, the processes of gold recovering from thiourea solutions have received little attention, particularly the electrowinning process. Gold electrowinning from thiourea solutions was studied by linear sweep voltammetry and chronopotentiometry. For potentials more cathodic than 0 mV vs. SCE gold reduction is mass transport controlled. The estimated diffusion Coefficient for the complex gold (I)-thiourea, at 25°C was 1.0 × 10−5, cm2s−1. The influence of gold, thiourea and formamidine disulfide concentrations on the cathodic behavior ofgold is described. A passivation due to thiourea adsorption on the electrode surface was observed at −300mV vs. SCE. Experiments shown that gold reduction is favored by low thiourea and formamidine disulfide concentrations. Chronopotentiometric measurements indicated the presence of an adsorption step before the reduction of the complex gold (I) -thiourea, although the reduction of the species in solution is also feasible. The influence of current density on the cathodic current efficiency and gold structure is presented.

Quantitative evaluation of protein recoveries in two-dimensional electrophoresis with immobilized pH gradients.

In this study, metabolically radiolabeled Escherichia coli cell extracts were used to systematically evaluate protein recoveries at each step of two-dimensional (2-D) electrophoresis and using different sample application methods. Sample application using sample cups resulted in better protein recovery compared with sample loading by rehydration when the Multiphor system was used. At least 50% or more of an E. coli extract was lost when high protein amounts (500 microg) were loaded by rehydration using this system, which employs separate holders for rehydration and isoelectric focusing (IEF). In contrast, when the IPGphor system was used, rehydration sample loading consistently yielded the highest overall protein recoveries. These improved protein recoveries were due to integration of rehydration and electrophoretic separation in a single unit. Even at high protein loads (500 microg), less than 15-20% of the proteins were lost when proteins were loaded by rehydration using sample buffer containing 2% carrier ampholytes in the ceramic immobilized pH gradient (IPG) strip holders used for both rehydration and IEF. Regardless of the loading conditions used, carrier ampholytes in the sample buffer increased protein recoveries. Use of thiourea did not significantly affect protein recoveries but did improve protein resolution in 2-D gels as expected. In summary, these results show the best protein recoveries are obtained for all protein loads when samples are applied to IPG strips during rehydration using a single device for both rehydration and IEF. In contrast, the poorest recoveries are obtained when rehydration and IEF are performed in separate devices, and losses increase dramatically with increasing protein loads using this approach.

Elimination of the memory effects of gold, mercury and silver in inductively coupled plasma atomic emission spectroscopy

The memory effects of mercury, gold and silver are eliminated by the use of sulfur containing complexing agents. In low concentrations (1 µg ml−1) of mercury and gold, the addition of 2% L-cysteine gives wash-out times of less than 1 min for both elements. At higher concentrations of gold and mercury, and at low concentrations of silver, the reagent is less effective. Thiourea, at a concentration of 1%, eliminates the memory effects of silver, also giving wash-out times of approximately 1.5 min. The use of thiourea with higher concentrations (100 µg ml−1) of mercury and gold delivers wash-out times of 1 min and 2 min, respectively. In a matrix similar to that found in many samples, the wash-out time for gold is less than 3.5 min and less than 2 min for mercury.

Use of thiourea to increase the solubility of membrane proteins in two-dimensional electrophoresis.

The separation of membrane proteins by high-resolution two-dimensional electrophoresis was carried out. At high loads, these proteins are prone to precipitation, resulting in poor resolution. It is shown here that the use of thiourea, previously described for focusing in immobilized pH gradients, can be extended to conventional isoelectric focusing. As thiourea inhibits acrylamide polymerization, a modified photopolymerization system must be used. These modifications result in higher solubility of proteins during IEF, thereby increasing the resolution and capacity of the two-dimensional gels.

Plasma protein adsorption patterns on emulsions for parenteral administration: establishment of a protocol for two-dimensional polyacrylamide electrophoresis.

The two-dimensional polyacrylamide electrophoresis (2-D PAGE) of the plasma protein adsorption pattern previously established for polymeric nanoparticles was modified and transferred to oil in water emulsions for intravenous administration. The emulsions were incubated with citrated plasma, and separation from excess plasma was performed by centrifugation under optimized conditions: 15000 g and three washing steps with 0.05 M phosphate buffer, pH 7.4. With this sample preparation, coalescence of droplets could be avoided and an unchanged surface area maintained, in addition the phosphate buffer minimized artificial IgG adsorption. Critical factors affecting sensitivity were contamination of the sample by oil residues and the use of thiourea in the immobilized pH gradients. Changes in the protein adsorption pattern caused by altered surface properties of the emulsion (i.e. adsorbed Poloxamer 407) were detectable when applying the optimized protocol. Knowledge of the protein adsorption patterns and their correlation to in vivo behavior opens the perspective for the development of intravenous emulsions for controlled drug delivery.