Copper(II) cyanido-bridged bimetallic nitroprusside-based complexes: Syntheses, X-ray structures, magnetic properties, Fe Mössbauer spectroscopy and thermal studies

Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN)₅NO]·H₂O (1), where tet=N,N′‐bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN)₅NO]·2H₂O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.1^6,9]octadecane and [Cu(nme)₂Fe(CN)₅NO]·H₂O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, ⁵⁷Fe Mössbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, ⁵⁷Fe Mössbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe₂O₄ and CuO.     

Simultaneous electrochemical determination of nitrate and nitrite in aqueous solution using Ag-doped zeolite-expanded graphite-epoxy electrode

In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1 M Na₂SO₄ supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10 mM for nitrate and 0.1-1 mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions.     

Carbon paste electrode for voltammetric detection of a specific DNA sequence from potentially aflatoxigenic Aspergillus species

An electrochemical biosensor for specific detection of DNA sequences from Aspergillus, a potentially aflatoxigenic fungus is reported. The detection technique was optimized using short DNA sequences, then applied for a 92-mer from the Aspergillus gene aflR that codes a biochemical pathway of aflatoxin B1 production.Voltammetric detection of the specific Aspergillus DNA sequence is based on hybridization of adsorbed target DNA with a biotinylated probe and subsequent binding with streptavidin alkaline phosphatase conjugate. Such modified electrode surface of carbon paste electrode (CPE) is incubated in a buffer with an electrochemically inactive substrate (1-naphthyl phosphate). Alkaline phosphatase converts 1-naphthyl phosphate into 1-naphthol, which is determined by the selected voltammetric technique. The optimized procedure provided good differentiation between complementary and noncomplementary probes and also between potentially aflatoxigenic and non-aflatoxigenic fungi of the genus Aspergillus.     

Synthesis, structure and solvatochromic properties of some novel 5-arylazo-6-hydoxy-4-phenyl-3-cyano-2-pyridone dyes

ABSTRACT: BACKGROUND: A series of some novel arylazo pyridone dyes was synthesized from the corresponding diazonium salt and 6-hydroxy-4-phenyl-3-cyano-2-pyridone using classical reaction for the synthesis of the azo compounds. RESULTS: The structure of the dyes was confirmed by UV-vis, FT-IR, 1H NMR, 13C NMR spectroscopic technique and elemental analysis. The solvatochromic behaviour of the dyes was evaluated with respect to visible absorption properties in various solvents. CONCLUSIONS: The azo-hydrazone tautomeric equilibration is found to depend upon substituents as well as on solvents. The geometry data of the investigated dyes were obtained using DFT quantum-chemical calculations. The obtained calculational results are in very good agreement with the experimental data.     

Effect of selenium in organic and inorganic form on liver,kidney, brain and muscle of <Emphasis Type="Italic">Wistar</Emphasis> rats

Selenium is a micronutrient, localized in the active sites of enzymes such as glutathione peroxidase and thioredoxin reductase, and participating together with these enzymes in an antioxidant defence system of organisms against free radicals. Administration of selenium is necessary for maintaining oxidative homeostasis. The present experiment is aimed at investigation of selenium impact on basal metabolic processes and selected antioxidants in a Wistar rat model, fed selenium in organic and inorganic forms. Liver, kidney, brain and muscle were sampled during a month-long feeding with four different doses of selenium (0.075 mg or 1.5 mg of inorganic and/or organic selenium per kg of feed). We found a significant reduction in glutathione level in liver tissue regardless of the form of the administered selenium. On the other hand, selenium caused a decreased glutathione reductase level in the liver and metallothionein level in the liver, kidney and muscle.      

Real-time monitoring of laser welding of galvanized high strength steel in lap joint configuration

Two different cases regarding the zinc coating at the lap joint faying surface are selected for studying the influence of zinc vapor on the keyhole dynamics of the weld pool and the final welding quality. One case has the zinc coating fully removed at the faying surface; while the other case retains the zinc coating on the faying surface. It is found that removal of the zinc coating at the faying surface produces a significantly better weld quality as exemplified by a lack of spatters whereas intense spatters are present when the zinc coating is present at the faying surface. Spectroscopy is used to detect the optical spectra emitted from a laser generated plasma plume during the laser welding of galvanized high strength DP980 steel in a lap-joint configuration. A correlation between the electron temperature and defects within the weld bead is identified by using the Boltzmann plot method. The laser weld pool keyhole dynamic behavior affected by a high-pressure zinc vapor generated at the faying surface of galvanized steel lap-joint is monitored in real-time by a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source.     

Radiatively generated maximal mixing scenario for the Higgs boson mass and the least fine-tuned minimal supersymmetric standard model

We argue that given the experimental constraints on the Higgs boson mass the least fine-tuned parameter space of the minimal supersymmetric standard model is with negative top-squark masses squared at the grand unification scale. While the top-squark mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs boson mass squared parameter from the running can be arbitrarily small, which reduces the fine-tuning of electroweak symmetry breaking. At the same time the top-squark mixing is necessarily enhanced and the maximal mixing scenario for the Higgs boson mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine-tuning is absent.     

Organocatalytic SOMO reactions of copper(I)-acetylide and alkylindium compounds with aldehydes

The derivatisation of aldehydes in their α-position is an important facet of organic synthesis. Organocatalytic radical reactions afford α-functionalised aldehydes via a SOMO activation pathway. New organo-SOMO reactions of aldehydes with copper(I)-acetylide and alkylindium reagents are detailed. These reactions proceed well under the catalysis of chiral imidazolidinones. The corresponding functionalised aldehydes were obtained with acceptable yields, but with only low enantiomeric ratios.     

Higher enantioselectivities in thiourea-catalyzed Michael additions under solvent-free conditions

Enantioselective Michael additions catalyzed by hydrogen-bonding catalysts produce many important compounds. Solvent-free reaction conditions in a ball mill can provide an improved enantioselectivity over the reaction in solution, due to lack of disruptive solvation of reagents. A range of 15 structurally different hydrogen-bonding organocatalysts were tested in two Michael additions to β-nitrostyrene under solvent-free conditions and compared with corresponding experiments in solution. With several thiourea catalysts, these Michael additions proceeded with higher enantioselectivities under solvent-free conditions than in solution.     

Study of Interaction between Metallothionein and CdTe Quantum Dots

Quantum dots (QDs) belong to a new class of fluorescent agent for biochemical, medicinal or other purposes. However, QDs based on cadmium or other metals can be risky for an organism. As one of the mechanism how to detoxify cadmium-based QDs expression of metallothioneins (MT) can be considered. Due to high affinity of metallothionein to cadmium(II) ions, we attempted to develop an approach for studying of possible interaction with QDs. We prepared QDs with CdTe core and studied the interaction with MT, which we isolated from livers of Cd-administered rabbits. To study the interaction, we used the mixture of both components MT (3.6 μM): CdTe QDs (0, 0.34, 0.68, 1.02, 1.36, 1.7, 2.04 and 2.47 μM). The mixtures were studied by spectrophotometry within the range from 200 to 750 nm with detected maxima at 260 and 505 nm. Same mixtures were also analysed by differential pulse voltammetry Brdicka reaction, which supported data from spectrophotometry. Subsequently, we used fast protein liquid chromatography for purification of protein–quantum dot conjugates. We obtained the different chromatograms for (1) Apo MT, (2) CdTe QDs and (3) MT–QD complex. We also collected the fractions and subsequently analysed them on the content of Cd and MT, which confirmed the formation of CdTe QDs–MT complex.