Functional copolymers with triazole and acetate fragments

New functional copolymers of different composition with triazole and acetate fragments in the macromolecules were synthesized by free radical copolymerization of 1-vinyl-1,2,4-triazole with vinyl acetate. The reactivity of the comonomers was studied and the monomer copolymerization constants were calculated. The structure and composition of the copolymers were determined by elemental analysis, IR and ¹H NMR spectroscopy.     

Fe-containing nanocomposites based on a biocompatible copolymer 1-vinyl-1,2,4-triazole with <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

New polymer nanocomposites containing iron oxide nanoparticles stabilized with a biocompatible copolymer of 1-vinyl-1,2,4-triazole with N-vinylpyrrolidone were produced. The synthesis was conducted using the method of chemical reduction of iron ions with hydrazine hydrate in an aqueous medium in the presence of a polymer matrix. The ESR spectroscopy data showed that the core—shell type nanoparticles were obtained. The core generally consistsed of zero-valence iron coated with an oxide shell. According to the data of transmission electron microscopy, the obtained polymer nanocomposites consisted of nanoparticles of mainly spherical shape with a diameter from 1 to 14 nm. Aggregates formed from individual stabilized nanoparticles of up to 75 nm in size (in most cases) were also observed. These aggregated particles were found to self-organize and form branched chains. Nanocomposites were characterized by a different particle-size distribution, which was determined by the initial ratio of the copolymer and the precursor of iron nanoparticles.     

Synthesis of complexes of N-vinylpyrrolidone–vinylamine or N-vinylpyrrolidone–allylamine containing macrocyclic polyligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) with gallium-68 isotope and estimation of their in vivo distribution

Russian Chemical Bulletin - A method for radiolabeling the water-soluble N-vinylpyrrolidone copolymers with N-vinyl- and N-allylamine containing bifunctional chelation unit...     

NO-donating and hemolytic activity of tetranitrosyl iron complexes with ligands of the 2-mercaptopyridine series

Russian Chemical Bulletin - The NO-donating and hemolytic activity of the binuclear tetranitrosyl iron complexes (TNIC) with thiolate ligands of the composition [Fe2(SR)2(NO)4], where R is...     

Gas-phase fragmentation studies of biotinylated oligomannuronopyranosides under conditions of collisionally activated dissociation

Russian Chemical Bulletin - High-resolution electrospray ionization mass spectra (MS and MS/MS) of a series of glycoconjugates containing biotin and oligomannuronopyranosyl residues linked via a...     

Carane amino alcohols as organocatalysts in asymmetric aldol reaction of isatin with acetone

Carane-derived β-amino alcohols with amino and hydroxy groups at positions 3 and 4 differing in their mutual arrangement and configuration were synthesized. Their application as organocatalysts in the asymmetric aldol reaction of isatin with acetone allowed one to obtain adducts with up to 84% enantiomeric excess.     

Checking of applicability of conditions for reaching the limiting-current mode to flow-by porous electrodes

For the flow-by porous electrodes, which differ in thickness, specific surface area, solution flow rate, and a ratio between the phase conductivities, the conditions providing the limiting-current mode over the entire electrode surface at nearly 100% current efficiency are determined using the method of successive refinement of total current and profile of its distribution along the solution flow. The used values of electrode thickness L are compared with available estimates for the limiting thickness of porous electrode L _lim derived for the ideal limiting-current mode and calculated using real values of the width of the limiting-current plateau of overall polarization curve, solution conductivity, and the diffusion limiting current in the zone of solution input into the electrode. It is found that these values are close to each other in all cases. The largest error of estimation of L _lim does not exceed 10% indicating that it can be used for preliminary estimation of the conditions for reaching the limiting-current mode for the flow porous electrodes of this type.     

Electrochemical oxidation of thrombin on carbon screen printed electrodes

The electrochemical oxidation of thrombin on the surface of carbon screen printed electrodes was studied. The electrochemical activity of thrombin was predicted, using bioinformation analysis, based on the data about the electrochemical properties of amino acids. The number of potentially electroactive amino acid residues, namely, tyrosine (Tyr), tryptophan (Trp), cysteine (Cys), histidine (His), methionine (Met), and cystine (Cys-Cys) located on the protein surface and orientated by their electroactive groups toward the electrode surface, i.e., accessible for electrochemical oxidation was calculated. The theoretical data were confirmed experimentally by cyclic and square-wave voltammetry. The available data on the protein structure allowed us to attribute the recorded electrochemical signals of thrombin oxidation to certain types of amino acid residue: the oxidation peak with a potential maximum at 0.7–0.8 V (vs. Ag/AgCl) was attributed to the oxidation of the Trp and Tyr residues; the wave in the range 1.0–1.2 V, to the oxidation of His; and the wave at 1.2–1.5 V, to the oxidation of Met and Cys-Cys. The electroanalysis based on the oxidation peak of the Tyr and Trp amino acid residues allowed to detect thrombin up to the concentration of 10^–7 M. The suggested strategy for predicting the electrochemical activity can be used for investigating the properties of many other proteins and peptides and serve as a basis for their quantitative determination when developing various sensor and biosensor devices.     

The synthesis,structure, and electrochemical properties of Li<Subscript>2</Subscript>FeSiO<Subscript>4</Subscript>-based lithium-accumulating electrode material

Different approaches to synthesis of Li₂FeSiO₄-based electrode materials for lithium intercalation, using low-cost and abundant Li-, Si-, and Fe-containing parent substances, are discussed. XRD, SEM, and a laser-diffraction analyzer of particle size were used for structure and morphology characterization of the composite electrode materials. Li₂FeSiO₄ was shown to be the main lithium-accumulating crystalline phase; minor LiFeO₂ and Li₂SiO₃ admixtures are also present. The material microparticles’ average size was shown to vary from tenths of micrometer to 1 μm. Larger objects sized ca. 2–4 μm are the microparticles’ agglomerates. The material electrochemical properties were studied by dc chronopotentiometry (galvanostatic charging–discharging) and cyclic voltammetry with potential linear sweeping. The initial reversible cycled capacity of the best samples is 170 mA h/g. The anodic and cathodic processes manifest obvious hysteresis caused by the presence of several different lithium ion energy states in the material; the transition between the states is kinetically hindered. The dependences of the specific capacity and its stability under cycling on the current load and the conductive carbon component content in the composite were elucidated.