Effect of dicitrato- and dimalatogermanic acids on polycondensation of maleic anhydride with ethylene glycol

The catalytic activity of citric (H₄Citr) and malic (H₃Mal) acids, their coordination compounds with germanium(IV) H₂[Ge(HCit)₂] and H₂[Ge(Mal)₂], and germanium dioxide GeO₂ in polycondensation of maleic anhydride and ethylene glycol at various temperatures was studied (catalyst: ethylene glycol molar ratio 0.01: 1). The process kinetics was evaluated and the time of its completion was determined. The copolymerization kinetics of some of the prepared oligoesters with triethylene glycol dimethacrylate was studied, and the copolymer properties were determined.     

Measuring the solubilities of ionic liquids in water using ion-selective electrodes

Polyvinyl chloride-plasticized membrane ion-selective electrodes (ISE) based on conventional ion-exchangers have been proposed as a cheap universal tool to measure the solubilities of ionic liquids (ILs) in water. They are applicable for ILs with a wide range of solubilities in water, since the linear range of a potentiometric response spans several orders of magnitude. As an example, we have fabricated and tested ISEs for widely used alkylimidazolium ionic liquids. The aqueous solubilities of four typical ILs have been determined at 21 °C: 0.075±0.001 mol l^–1 (1-butyl-3-methylimidazolium, BMIm, hexafluorophosphate); 0.018±0.001 mol l^–1 (BMIm bis(triflylimide)); 0.054±0.007 mol l^–1 (1-butyl-2,3-dimethylimidazolium, BDMIm, hexafluorophosphate); 0.014±0.001 mol l^–1 (BDMIm bis(triflylimide)).     

Determination of β-Lactam Antibiotics by Potentiometry with Ion-Selective Electrodes

Ion-selective electrodes for antibiotics from the penicillin series, with membranes based on three different classes of ionophores (anion exchangers, aza compounds, and metal phthalocyanines), were proposed. The electrochemical and performance characteristics of the sensors were studied and compared.     

Application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry for the study of Helicobacter pylori

The characteristics of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry based investigation of extremely variable bacteria such as Helicobacter pylori were studied. H. pylori possesses a very high natural variability. Accurate tools for species identification and epidemiological characterization could help the scientific community to better understand the transmission pathways and virulence mechanisms of these bacteria. Seventeen clinical as well as two laboratory strains of H. pylori were analyzed by the MALDI Biotyper method for rapid species identification. Mass spectra collected were found containing 7–13 significant peaks per sample, and only six protein signals were identical for more than half of the strains. Four of them could be assigned to ribosomal proteins RL32, RL33, RL34, and RL36. The reproducible peak with m/z 6948 was identified as a histidine‐rich metal‐binding polypeptide by tandem mass spectrometry (MS/MS). In spite of the evident protein heterogeneity of H. pylori the mass spectra collected for a particular strain under several cultivations were highly reproducible. Moreover, all clinical strains were perfectly identified as H. pylori species through comparative analysis using the MALDI Biotyper software (Bruker Daltonics, Germany) by pattern matching against a database containing mass spectra from different microbial strains (n = 3287) including H. pylori 26695 and J99. The results of this study allow the conclusion that the MALDI‐TOF direct bacterial profiling is suited for H. pylori identification and could be supported by mass spectra fragmentation of the observed polypeptide if necessary. Copyright © 2010 John Wiley & Sons, Ltd.     

Calculation of alkaline metal dimers in terms of model perturbation theory

The problem of calculating diatomic alkaline metal (homo- and heteronuclear) molecules KM (M=Li, Na, K, Rb, Cs) is treated in terms of a pseudopotential approach in the framework of a formally exact model perturbation theory of Rayleigh-Schrödinger type with a test zero-order potential. A Gell-Mann type local model potential is used as a zero-order potential. The results of calculations of energy parameters, in particular, dissociation energies, are given; some of them were obtained for the first time. The calculation demonstrated that two major effects of second-order perturbation theory: polarizing interaction of valence particles across the core and mutual screening of particles must be taken into account to achieve an acceptable accuracy of calculations.     

Aqueous biphasic systems formed by nonionic polymers I. Effects of inorganic salts on phase separation

The effect of salts KSCN, KI, KBr, KCl, KClO₄, KF, K₂SO₄ and NH₄Cl, LiCl, NaCl, KCl, CsCl on the binodials of the phase diagrams for aqueous biphasic dextranpolyvinylpyrrolidone, dextran-polyvinyl alcohol, dextran-ficoll and dextran-polyethylene glycol systems was studied. It is established that the K-salts present at the concentrations of 0.1 and 0.5 mol/kg alter the binodials of the phase diagrams for the above systems. The effect of a salt is found to be related to the lyotropy of the salt quantified by the salt molal surface tension increment. It is assumed that phase separation in an aqueous polymer biphasic system is affected by the presence of a salt mainly due to the effect of the salt on the structure and/or state of water in the system.     

Software for precision x-ray diffraction studies

Moscow Chemical Engineering Institute. Institute of Heteroorganic Compounds. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 1, pp. 170–171, January–February, 1991.     

Structure and properties of aqueous dispersions of sodium dodecyl sulfate with carbon nanotubes

The dispersing action of the surfactant (sodium dodecyl sulfate, SDS) on the carbon nanotubes (CNT) in aqueous medium has been studied. Electron microscopy, molecular docking, NMR and IR spectroscopies were applied to determine the physical-chemical properties of CNT dispersions in SDS—water solutions. It was established that micellar adsorption of the surfactant on the surface of carbon material and solubilization of SDS in aqueous medium contribute to improving CNT dispersing in water solutions. It was shown that the non-polar hydrocarbon radicals of a single surfactant molecule form the highest possible number of contacts with the graphene surface. Upon increase of the SDS in solution these radicals form micelles connected with the surface of the nanotubes. At the sufficiently high SDS concentration the nanotube surface becomes covered with an adsorbed layer of surfactant micelles. Water molecules and sodium cations are concentrated in spaces between micelles. The observed pattern of micellar adsorption is somewhat similar to a loose bilayer of surfactant molecules.     

Calculation of the spectroscopic characteristics of the dimers of alkali elements on the basis of a model perturbation theory

Based on pseudopotential approach within the model, formally accurate perturbation theory of the Rayleigh–Schrödinger type with a zero-approximation priming potential, a problem of calculation of some alkaline diatomic molecules is considered in homo- and heteronuclear variants of Na₂ and RbM (M=Na, Li, K, Rb, Cs). The results of calculation of the energy parameters, in particular, the dissociation energies, are given; some of the data were obtained for the first time. The results of the calculation for the energies of Rydberg states $n^1 \sum\nolimits_g^ + {(n = 4 - 6)} $ and spectroscopic constants of the Na dimer are given. The calculation demonstrated the important role, in attainment of acceptable accuracy, of two basic 2nd order effects in the theory of perturbations, i.e., the effect of polarization interaction of valence particles through the core and the effect of their screening by one another. For Rydberd states, the contribution of core excitations turns out to be important.