Laccase-Catalyzed Heterocoupling of Dihydroquercetin and p-Aminobenzoic Acid: Effect of the Reaction Product on Cultured Cells.

Derivatization of the natural flavonoid dihydroquercetin with p-aminobenzoic acid was carried out in an ethyl acetate/citric buffer biphasic system using laccase from the fungus Trametes hirsuta. The main reaction product yield was ~68 mol %. The product was characterized by 1H NMR, 13C NMR, and liquid chromatography-mass spectroscopy, and its structure was elucidated. The reaction product affected viability of cultured human rhabdomyosarcoma cells (RD cell line) in a dose-dependent manner and, therefore, can be of interest to pharmaceutical industry.

[Dihydroquercetin polymerization using laccase immobilized into an ionic liquid].

It was shown that the laccase (LC) included into hydrophobic ionic liquid (IL) can be reused for the biotransformation of dihydroquercetin (DHQ). The physicochemical characteristics of DHQ oligomers synthesized using LC/IL did not differ from the characteristics of the oligomers obtained with native laccase. The synthesized oligomers have a number average molecular weight of 1050 g/mol and a polydispersity index of 1.41. Oligomers possess higher antioxidant activity than the monomer.

[Aniline Polymerization on Multiwall Carbon Nanotubes with Immobilized Laccase].

A composite material consisting of electrically conductive polyaniline deposited on the surface of multiwall carbon nanotubes has been synthesized. Enzymatic synthesis was carried out in the presence of Trametes hirsuta laccase immobilized on the nanotube surface. The obtained composite was morphologically uniform, and its electrochemical capacity and stability were much higher than those of a composite synthesized according to the conventional chemical procedure.

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 (1)H and (13)C 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.

Impact of surface modification with gold nanoparticles on the bioelectrocatalytic parameters of immobilized bilirubin oxidase.

We unveil experimental evidence that put into question the widely held notion concerning the impact of nanoparticles on the bioelectrocatalytic parameters of enzymatic electrodes. Comparative studies of the bioelectrocatalytic properties of fungal bilirubin oxidase from Myrothecium verrucaria adsorbed on gold electrodes, modified with gold nanoparticles of different diameters, clearly indicate that neither the direct electron transfer rate (standard heterogeneous electron transfer rate constants were calculated to be 31±9 s(-1)) nor the biocatalytic activity of the adsorbed enzyme (bioelectrocatalytic constants were calculated to be 34±11 s(-1)) depends on the size of the nanoparticles, which had diameters close to or larger than those of the enzyme molecules.

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.

[An electrochemical method for measuring metabolic activity and counting cells].

An express electrochemical method for determining the metabolic activity of live cells based on the possibility of an electron exchange between an electrode and elements of the biological electron transfer chain in the presence of a mediator is proposed. This method is useful for studying any live cells (animal, plant, and microbial), including anaerobic, dormant, and spore cells. The sample preparation and measurement itself does not take more than 30 min. The detection limit in a volume of 15 ml amounts to 10-5 cells/ml. The applicability of the assessment method of the metabolic activity level during the transition of the bacteria Mycobacterium smegmatis into an uncultivable dormant state was demonstrated. This method is of special value for medicine and environmental control, detecting latent forms of pathogens. An optimal combination of the methods for the express analysis of latent pathogens is proposed.