Fourier Transform Infrared (FTIR) Spectroscopic Analyses of Microbiological Samples and Biogenic Selenium Nanoparticles of Microbial Origin: Sample Preparation Effects

To demonstrate the importance of sample preparation used in Fourier transform infrared (FTIR) spectroscopy of microbiological materials, bacterial biomass samples with and without grinding and after different drying periods (1.5–23 h at 45 °C), as well as biogenic selenium nanoparticles (SeNPs; without washing and after one to three washing steps) were comparatively studied by transmission FTIR spectroscopy. For preparing bacterial biomass samples, Azospirillum brasilense Sp7 and A. baldaniorum Sp245 (earlier known as A. brasilense Sp245) were used. The SeNPs were obtained using A. brasilense Sp7 incubated with selenite. Grinding of the biomass samples was shown to result in slight downshifting of the bands related to cellular poly-3-hydroxybutyrate (PHB) present in the samples in small amounts (under ~10%), reflecting its partial crystallisation. Drying for 23 h was shown to give more reproducible FTIR spectra of bacterial samples. SeNPs were shown to contain capping layers of proteins, polysaccharides and lipids. The as-prepared SeNPs contained significant amounts of carboxylated components in their bioorganic capping, which appeared to be weakly bound and were largely removed after washing. Spectroscopic characteristics and changes induced by various sample preparation steps are discussed with regard to optimising sample treatment procedures for FTIR spectroscopic analyses of microbiological specimens.     

New mesomorphic organocyclosiloxanes II. Thermal behaviour and mesophase structure of organocyclohexasiloxanes

Investigations of thermotropic phase transitions performed on organocyclosiloxanes [PhSi(O)OSiR]₆, where R is Me₃, Me₂(CH₂Cl) or Me₂(CH≃CH₂), have revealed that all these hexamers are mesomorphic compounds. The hexamers exhibit uncommon polymesomorphic behaviour forming two quite different mesomorphic structures. The molecular arrangement in the low temperature (LT) modification is characterized by two-dimensional (2D) long-range order with hexagonal packing. The X-ray diffraction pattern and peculiarities of molecular packing in the crystal lead us to suggest that the LT-mesophase is columnar, presumably of the Col_hd type. The LT-mesophase is formed by dimeric moieties, which associate with each other in column-like substructures, the ring planes not orthogonal to the stack axis. The high temperature (HT) mesophase is a plastic crystal (3D-order), where molecules take up positions in a face-centred cubic lattice. This is a very uncommon example of thermal behaviour for plastic crystals that provides a unique opportunity to bridge the gap between plastic crystalline and liquid crystalline mesomorphic behaviour. The thermal and structural properties of the mesophases depend upon the type of side groups of the hexamers. The size of the ring also affects the phase behaviour and the mesomorphic structure. This conclusion is consistent with data obtained by us earlier for cyclotetrasiloxanes.     

Invariants of multi-parameter approximate transformation groups

The problem of finding all functionally independent invariants for a given multi-parameter approximate transformation group is considered. The criterion for approximate function to be invariant under an approximate transformation group is similar to that of Lie's theory and is based on operators of the corresponding approximate Lie algebra. The calculation of invariants of an approximate transformation group reduces to solving the system of linear nonhomogeneous first-order PDEs. The sufficient conditions of compatibility and completeness for these systems are proved.     

Dinuclear copper(ii) complex with novel N,N’,N”,O-tetradentate Schiff base ligand containing trifluoromethylpyrazole and hydrazone moieties

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4-Hydroxyproline containing podands as new chiralcatalysts for the asymmetric Biginelli reaction

The novel C₂-symmetric chiral organocatalysts of (2S,4R)-hydroxyproline containing podand type have been synthesized and evaluated in the asymmetric Biginelli reaction. Combination of polyether spacer with (2S,4R)-hydroxyproline allowed one to enhance the effect of the latter on enantioselectivity of the Biginelli reaction by a factor of 5. The best results have been achieved for salts of (2S,4R)-hydroxyproline containing podands with trifluoroacetic acid.

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Determination of Rh(III) by stripping voltammetry on a graphite electrode modified with lead

Journal of Solid State Electrochemistry - The process of electrooxidation of a lead-rhodium binary deposit on a graphite electrode has been studied. The anodic voltammetric curves show the peak of...     

Synthesis and antiproliferative evaluation of glucosylated pyrazole analogs of K252c

Pyrazole analogs of the staurosporine aglycon K252c were recently described as potent inhibitors of the three Pim protein kinase isoforms. To evaluate the impact of the introduction of a sugar moiety on the biological activities of this heterocyclic scaffold, four new glucosylated pyrazole analogs of K252c were synthesized. Their biological evaluation demonstrated that most active compounds 11 and 19 substituted by a β-d-glucosyl moiety at N12 or N13 positions exhibited antiproliferative activities toward HCT116 cells.     

Thermodynamic properties of chitosan-based hydrogels in the range 0–350 K

The heat capacity, the temperature, and the enthalpy of physical transformations of hydrogels based on the copolymer of acrylamide and chitosan with N,N-methylene-bis(acrylamide) as a crosslinking agent, hydrogels based on the mixture of poly(vinylpyrrolidone) and chitosan with glutaric aldehyde as the crosslinking agent, and dehydrated hydrogels has been studied in the range 85–350 K with the use of adiabatic vacuum calorimetry. The temperatures and enthalpies of melting of free water in hydrogels have been determined. From the experimental data obtained, the thermodynamic functions C° _p (T), H° (T) ? H°(0), S° (T) ? S°(0), and G° (T) ? H°(0) have been calculated for the temperature range 0–350 K. The ratio of free and bound water in the hydrogels under study has been determined by calorimetry.