Structural and conformational properties of 2-propenylgermane (allylgermane) studied by microwave and infrared spectroscopy and quantum chemical calculations

The structural and conformational properties of allylgermane have been investigated using Stark and Fourier transform microwave spectroscopies, infrared spectroscopy, and high-level quantum chemical calculations. The parent species H2C=CHCH2GeH3 was investigated by microwave spectroscopy and infrared spectroscopy, while three deuterated species, namely, H2C=CDCH2GeH3, H2C=CHCHDGeH3, and H2C=CHCH2GeD3, were studied only by infrared spectroscopy. The microwave spectra of the ground vibrational state as well as of the first excited state of the torsion vibration around the sp2-sp3 carbon-carbon bond were assigned for the 70Ge, 72Ge, and 74Ge isotopomers of one conformer. This rotamer has an anticlinal arrangement for the C=C-C-Ge chain of atoms. The infrared spectrum of the gas in the 500-4000 cm(-1) range has been assigned. No evidence of additional rotameric forms other than anticlinal was seen in the microwave and infrared spectra. Several different high-level ab initio and density functional theory calculations have been performed. These calculations indicate that a less stable form, having a synperiplanar conformation of the C=C-C-Ge link of atoms, may coexist with the anticlinal form. The energy differences between the synperiplanar and anticlinal forms were calculated to be 5.6-9.2 kJ/mol depending on the computational procedure. The best approximation of the equilibrium structure of the anticlinal rotamer was found in the MP2/aug-cc-pVTZ calculations. The barrier to internal rotation of the germyl group was found to be 6.561(17) kJ/mol, from measurements of the splitting of microwave transitions caused by tunneling of the germyl group through its threefold barrier.     

Synthesis and properties of NiSn colloids using different metal ratios by CLD

Bimetallic colloidal dispersions of Ni–Sn were prepared by simultaneous co-condensation with organic solvents at 77 K using the chemical liquid deposition (CLD) method. The atoms in a 1:1, 2:1, 3:1, 1:2 and 1:3 ratios were produced by resistive heating and were reacted with 2-propanol, 2-methoxyethanol, ethanol and acetone to produce colloids. The bimetallic films and solids were obtained by evaporation under vacuum at room temperature. The colloids and solids were characterized by several studies, including the stability at room temperature, electrophoresis, ultraviolet-visible spectrophotometry, transmission electron microscopy (TEM), electron diffraction, conductivity, nergy dispersive X-ray analysis, electrophoretic measurements, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and magnetic properties. TEM studies show a size distribution between 6 and 14 nm, depending of the solvent and Ni:Sn ratio. We can observe a high stability for the colloidal dispersion with different solvents (>2 weeks); this is due mainly to the solvation capacity and polarity of the organic molecules. Electrophoretic measurements revealed that the particles are weakly positively charged with a greater Ni percentage. Electron diffraction analysis for the metallic colloids shows the presence of bimetallic compounds as NiSn, Ni₃Sn, Ni₃Sn₄ and tin oxides. XPS analysis was used for the study of the Ni–Sn solid composition, where it was determined that the Ni atoms could be as Ni⁰ and Ni²⁺. The bond energy difference in both species were 0.8 eV; on the other side, Sn atoms showed two peaks, the first associated with Sn⁰ atoms and the second attributed to oxidized species like SnO_x. The conductivity studies showed that when the metal is changed, the electric conductivity properties change too and are associated with the particle size increasing.     

Production and Characterization of F(Ab’)<Subscript>2</Subscript> Fragments Obtained by Enzymatic Digestion from Murine Anti-MRSA PBP2a Monoclonal Antibodies

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a worldwide health problem. In a previous study, a murine monoclonal antibody (mMAB), capable of binding to PBP2a within MRSA strains, was generated. F(ab’)₂ antibody fragments are widely described in the literature as immunochemical tools and reagents for diagnostics and therapeutics, particularly because of their low immunogenicity and rapid pharmacokinetics. In this study, F(ab’)₂ fragments from mMAB were generated by enzymatic digestion, using pepsin. They were purified by affinity chromatography using protein A and concentrated by a MWCO 50 kDa filtration unit. The results indicate that it is possible to obtain F(ab’)₂ fragments by pepsin digestion. ELISA, western blotting, and fluorescence microscopy data demonstrated that F(ab’)₂ affinity for PBP2a is not lost even after the enzymatic digestion process. As expected, in the pharmacokinetics tests, F(ab’)₂ presented a faster elimination (between 12 and 18 h) compared to IgG. These F(ab’)₂ fragments could be used in future immunodiagnostic applications, including in vitro or in situ radiolabeling and in the treatment of infections caused by this important pathogen.     

Determination of amitrole and urazole in water samples by capillary zone electrophoresis using simultaneous UV and amperometrical detection

In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was first applied to the simultaneous separation and determination of amitrole and urazole in water samples. A simple end-column electrochemical detector was used in combination with a commercially available capillary electrophoresis instrument with UV detection. The effects of several important factors were investigated to find optimum conditions. A carbon disk electrode was used as working electrode. Separation and determination of these compounds in water samples were performed in 0.030 mol l(-1) acetate buffers at pH 4.5, 25 kV as separation voltage and the samples were introduced by hydrodynamic mode for 1.5 s. Most of the studies realized showed that the direct electrochemical detection is more sensitive and selective than UV detection. Under the optimum conditions, excellent linearity was observed between peak amperometric signal and analyte concentrations in the range of 0.19-1.35 mg l(-1) for amitrole and 0.20-1.62 mg l(-1) for urazole. The detection limits were 63 and 68 microg l(-1) for amitrole and urazole, respectively. The utility of this method was demonstrated by monitoring water samples, and the assay results were satisfactory. The detection limits using a previous preconcentration step for amitrole and urazole in spiked mineral water samples were 0.6 and 1.0 microg l(-1) for amitrole and urazole, respectively.     

Optimisation of headspace solid-phase microextraction for the analysis of volatile phenols in wine

Headspace solid-phase microextraction has been applied to the analysis of volatile phenols in wine. Silica fibre coated with Carbowax-divinylbenzene was found to be more efficient at extracting these compounds than other fibres such as those coated with polydimethylsiloxane, polyacrylate, carboxen-polydimethylsiloxane, and polydimethylsiloxane-divinylbenzene. Different parameters such as extraction time, temperature of the sample during the extraction, ionic strength and sample volume were optimised using a two-level factorial design expanded further to a central composite design, in order to evaluate several possibly influential and/or interacting factors. The headspace (HS)-SPME procedure developed shows adequate detection and quantitation limits, and linear ranges for correctly analysing these compounds in wine. The recoveries obtained were close to 100%, with repeatability values lower than 16%. The method was applied to a variety of white and red wines.     

Comparative analysis of the organic acid content of vinegar by capillary electrophoresis and ion-exclusion chromatography with conductimetric detection

Summary Ion-exclusion chromatography (IEC) and capillary electrophoresis (CE) have been compared for determination of organic acids in samples of Sherry wine vinegar. The accuracy of each technique was evaluated by use of the standard addition method. There were no differences between the techniques at a significance level of 5%, except for determination of malic acid by CE. Both analytical methods were used to analyse sixteen samples of Sherry wine vinegar supplied by different producers. The regression coefficients (r ²) for analysis by IEC and CE exceeded 0.94 for all acids. Results from both methods were in good agreement and the methods are sufficiently selective and sensitive to be applied directly to sherry wine vinegars.     

Haematoporphyrin derivative (Photofrin II) photosensitization of isolated mitochondria: inhibition of ADP/ATP translocator

To gain further insight into the mechanism by which irradiation of mitochondria in the presence of haematoporphyrin derivative (Photofrin II) (PF II) causes impairment of mitochondrial oxidative phosphorylation, the rate of ADP/ATP exchange via the ADP/ATP translocator was measured fluorometrically is isolated rat liver mitochondria. In accord with noncompetitive inhibition, PF II photosensitization decreases the maximum rate of exchange Vmax (20.8 and 9.6 nmol ATP effluxed min-1 x mg protein in the control and after 2 min irradiation, respectively) without changing the ADP affinity for the carrier (Km = 5 microM in both cases). Comparison of the rate of oxygen uptake by mitochondria stimulated by either ADP or by the uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) confirms that the adenine nucleotide carrier is a major target of photodynamic action which causes oxidative phosphorylation impairment.