I. S. Vasil’eva

Biocatalytic synthesis of conducting polymers and prospects for its application

Enzymatic methods of synthesis of conducting polymers, physicochemical properties of the resulting products, and mechanisms of the reactions are considered. The enzymes involved in oxidative polymerization of monomers are briefly characterized. Examples of practical application of enzymatically synthesized conducting polymers are given.

Use of aqueous hydrogen peroxide solutions prepared by cathodic reduction of oxygen for indirect oxidation of chemical substances in situ: Achievements and prospects

The achievements and prospects in the use of aqueous hydrogen peroxide solutions prepared by cathodic reduction of oxygen in carbon black gas-diffusion and graphite electrodes for indirect oxidation of organic and inorganic substrates in situ are analyzed. Specific examples demonstrate the efficiency of using hydrogen peroxide solutions for in situ indirect electrocatalytic oxidation of organic and inorganic substrates to target products (indirect electrochemical synthesis), for decomposition (mineralization) of organic and inorganic pollutants in industrial waters and wastewaters, and for preparation of organic peroxy acids and inorganic peroxy solvates.

Synthesis of electroconductive polyaniline using immobilized laccase

A new method for synthesis of the conductive complex between polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPS) was proposed; in this method, the immobilized laccase from the basidiomycete Trametes hirsuta is used as a biocatalyst for aniline oxidative polymerization. The conditions for laccase immobilization on CM cellulose by bifunctional Woodward’s reagent were optimized. The catalytic properties of immobilized and native laccases were compared. The immobilized laccase appeared an efficient catalyst for the oxidative radical polymerization of aniline on polysulfonic acid matrix at 4°C. It was demonstrated that the immobilized enzyme could be repeatedly used for enzymatic synthesis of this polymer. Several spectral characteristics of the PANI/PAMPS complexes synthesized at various pH values were studied. The conductance of PANI specimens produced using immobilized laccase as a catalyst was 13 mS/cm.

Enzymatic polymerization of dihydroquercetin using bilirubin oxidase

Dihydroquercetin (or taxifolin) is one of the most famous flavonoids and is abundant in Siberian larch (Larix sibirica). The oxidative polymerization of dihydroquercetin (DHQ) using bilirubin oxidase as a biocatalyst was investigated and some physicochemical properties of the products were studied. DHQ oligomers (oligoDHQ) with molecular mass of 2800 and polydispersity of 8.6 were obtained by enzymatic reaction under optimal conditions. The oligomers appeared to be soluble in dimethylsulfoxide, dimethylformamide, and methanol. UV-visible spectra of oligoDHQ in dimethylsulfoxide indicated the presence of highly conjugated bonds. The synthesized oligoDHQ was also characterized by FTIR and 1H and 13C NMR spectroscopy. Comparison of NMR spectra of oligoDHQ with DHQ monomer and the parent flavonoids revealed irregular structure of a polymer formed via the enzymatic oxidation of DHQ followed by nonselective radical polymerization. As compared with the monomer, oligoDHQ demonstrated higher thermal stability and high antioxidant activity.

Adaptogenic Effects of Furostanol Glycosides of Dioscorea deltoidea Wall on Oxidative Processes in Tomato Plants during Biotic Stress

The effect of furostanol glycosides of a cell culture of Dioscorea deltoidea Wall on oxidative processes in tomato plants subjected to invasion with the gall nematode Meloidogyne incognita Kofoid et White was studied. We showed that furostanol glycosides induce a nonspecific defensive response in plants. Exposure of cell membranes to furostanol glycosides causes rearrangements in fatty acids, resulting in the formation of conjugated dienes, which makes molecules thermodynamically more stable under stress conditions. The study of changes in the activity of peroxidases of intact plants and plants affected with the nematode, which were treated with furostanol glycosides, showed that the protective effect of the guaiacol-dependent peroxidase is more long-term than the effect of the benzidine-dependent peroxidase.

Enzymatic synthesis of electroconductive biocomposites based on DNA and optically active polyaniline

Electroconductive interpolymer polyaniline complexes are synthesized on the DNA matrix, using the method of oxidative polymerization of aniline with two different biocatalyzers: horseradish root peroxidase and micropiroxidase-11 biomimetic. The spectral characteristics and morphology of the acquired biocomposites have been studied. The stereospecificity of the acquired samples of interpolymer complexes is shown, depending on the biocatalyzers used. The results acquired indicate the important role of a biocatalyzer in the formation of the twist direction of an electroconductive polymer spiral on the DNA matrix; i.e., the optical activity of the polymer samples acquired is apparently associated with the biocatalyzer properties.

Effects of the composition of acid solutions and the presence of organic acids on oxygen electroreduction to hydrogen peroxide in a carbon black gas-diffusion electrode

This paper reports on the effects of the K2SO4, H2SO4, NaCl, HCl, and tetrabutylammonium bromide concentrations (0.01–0.0002 M) and the presence of formic, acetic, and butyric acids in the electrolyte on the kinetic characteristics of oxygen reduction to H2O2 in a carbon black gas-diffusion electrode (GDE) and on the H2O2 accumulation kinetics in electrolyte at current densities of 30–100 mA/cm2. The introduction of K2SO4 and tetrabutylammonium bromide in the electrolyte led to an increase in the transfer coefficient α and a decrease in the coefficients in the Tafel equation. The concentration and the current efficiency of H2O2 decreased with the salt to acid concentration ratio. The organic acids reduced the current efficiency of H2O2 and increased the electrode polarization. Peracids with a current efficiency of up to 0.27% and concentration of up to 7.5 mM were obtained. Solutions of H2O2 with concentrations of 0.6–3.3 M and current efficiencies of 17–75% were obtained at current densities of 30–100 mA/cm2 in electrolytes with salt and inorganic acid concentrations of 0.9–40 g/l and in the presence of organic acids.

Formation of peracids from corresponding organic acids under oxygen electroreduction in gas-diffusion electrode

The effect of conditions of electrolysis in aqueous solutions of (K2SO4 + H2SO4) electrolytes was studied in the presence of formic, acetic, and butyric acids on the formation of the corresponding peracids under oxygen electroreduction in carbon black gas-diffusion electrodes. In the presence of organic acids with the concentration of 1.5–4.7 M, as dependent in the electrolysis conditions, the current efficiency of H2O2 formation decreases from 70 to 13 % and its concentration drops from 2.3 to 0.4 M. Electrolysis under constant current (50–100 mA/cm2) results in formation of peracids with the concentration of up to 7.5 mM. No direct dependence of the concentration of peracids on the concentration of the obtained H2O2 is observed. The presence of tetrabutylammonium bromide in the solution inhibits significantly peracid formation. It is assumed that synthesis of peracids occurs partly on the surface of carbon black through activation of the adsorbed acid by a hydrogen cation and further interaction with the active form of oxygen obtained under oxygen reduction or decomposition of H2O2.

Steroid furostanol glycosides: A new class of natural adaptogenes (Review)

The present review summarizes experimental data revealed while studying the mechanism of the adaptogenic effect of furostanol glycosides (FG) extracted from Dioscorea deltoidea Wall cell culture under the conditions of biotic stress in tomato plants Lycopersicon esculenium Mill. induced by the gall nematode Meloidogyne incognita Kofoid et White. Comparison of changes in isoprene content (phytosterines, tomatin, and carotenoids) and in the rate of oxidative processes in the leaves and roots of intact and treated plants evidence that FG cause nonspecific defense reactions resulting in the formation of systemic acquired resistance. This formation is presented by the enhancement in photosynthetic apparatus pigment fund, pigments of the violaxanthin cycle in particular, by activation of processes related to POL, and by increase in peroxidase activity—enzyme of antioxidant protection.

Removal of heavy metal ions from aqueous solutions by electrocoagulation using Al and Fe anodes

Electrocoagulation treatment of model wastewater solutions to remove jointly present Cu2+ and Ni2+ ions was studied. The influence of the current density, concentration of impurities, anode material, and structure of the precipitate of coagulant metal hydroxides on the efficiency of removal of the heavy metal ions was examined. The decisive factor under the chosen process conditions is the anode material. The electrocoagulation efficiency is considerably higher when using the aluminum anode, compared to the iron anode.