Sergei D. Varfolomeyev

THE ELECTROCHEMICAL POLYMERIZATION OF METHYLENE-BLUE AND BIOELECTROCHEMICAL ACTIVITY OF THE RESULTING FILM

Abstract The electrochemical polymerization of methylene blue in aqueous solutions and the properties of the resulting films were investigated. The films possessed monomer-type redox activity, and a new redox couple, responsible for the semiconducting properties of the polymer, was observed. The growth rate of the film increased in basic media. The influence of hydroxide ions can be simulated in terms of both nucleophilic catalysis and a shielding effect. The bioelectrochemical oxidation of glucose at methylene blue semiconductor films in the presence of glucose oxidase was observed.

Hydrogen fuel electrode based on bioelectrocatalysis by the enzyme hydrogenase

Abstract Our aim is to show, that the enzymes as electrocatalysts are able to improve the performance characteristics of the fuel cells. The hydrogen fuel electrode based on hydrogenase from Thiocapsa roseopersicina immobilized directly on carbon filament material has been made. The enzyme electrode has operated according to electron tunneling between the enzyme active site and the electrode support; this mechanism is called direct bioelectrocatalysis. Under pure hydrogen the efficiencies in energy conversion of the enzyme electrode and the noble metal based commercial fuel electrode are similar concerning both the hydrogen equilibrium potential achieved and the current densities in H2 oxidation. However, the use of the enzyme electrodes completely avoids the problem of poisoning the anode by the impurities of carbon monoxide present in reforming gas, which limits the use of cheap hydrogen containing fuel. The stability of the biological catalysts can be drastically improved by their immobilization on electrode supports, which provide the development of commercially competitive biofuel cells.

Non-aqueous enzymology approach for improvement of reagentless mediator-based glucose biosensor

The formation of Nafion membranes containing glucose oxidase and dimethylferrocene as a mediator was optimized using a previously reported non-aqueous enzymology approach for biosensor development. Enzyme immobilization in Nafion membranes was carried out from water-organic mixtures with a high content of organic solvent. The mediator based reagentless glucose electrode was tested in a flow injection system. The response towards glucose addition was stable: the reproducibility during 50 assays exceeded 95%. The response was linear over the glucose concentration range 0.5-50 mM.

Addition of Polybrene improves stability of organophosphate hydrolase immobilized in poly(vinyl alcohol) cryogel carrier

Organophosphate hydrolase, covalently attached to the beads of poly(vinyl alcohol) cryogel in the presence of Polybrene, was fivefold more stable in 15% (v/v) ethanol solution than the free enzyme. Immobilized biocatalyst, prepared with an addition of Polybrene, retained a half of its initial activity in 50% (v/v) aqueous ethanol solution, 90% of activity during 10 working cycles of Paraoxon hydrolysis and 85% of activity after storage in the 50 mM CHES buffer (pH 9.0) at room temperature for 2 months.

The electrochemical polymerization of Methylene Blue and bioelectrochemical activity of the resulting film

Abstract The electrochemical polymerization of Methylene Blue in aqueous solutions and the properties of the resulting films were investigated. These films possessed monomer-type redox activity. In addition, a new redox couple, responsible for polymer semiconductor properties, was observed. Film growth rate increased in basic media. The hydroxide ion influence could be simulated in terms of both nucleophilic catalysis and shielding effect. Bioelectrochemical glucose oxidation took place at Methylene Blue semiconductor films in the presence of glucose oxidase.

Double effect of organic amines (activation and inhibition) on the phosphotriesterase

Abstract The kinetic behavior of the phosphotriesterase in the presence of organic amines (diethylamine, diisopropylamine, triethylamine, pyridine and others) capable of activating the enzyme at the concentration up to 0.10 M and inhibiting it at higher concentrations is described. The form acting as activator in a solution is the nonprotonated form of amines and the value of activation effect depends on p K a of amine and its structure. The activation by amines at the above concentrations has a noncompetitive character, whereas the inhibition at higher concentrations has competitive one. The mechanism of phosphotriesterase action in the presence of amines is discussed.

Interaction of Escherichia coli inorganic pyrophosphatase active sites

Escherichia coli inorganic pyrophosphatase (PPase) is a hexamer of identical subunits. This work shows that trimeric form of PPase exhibits the interaction of the active sites in catalysis. Some trimer subunits demonstrate high substrate binding affinity typical for hexamer whereas the rest of subunits reveal more than 300‐fold substrate affinity decrease. This fact indicates the appearance of negative cooperativity of trimer subunits upon substrate binding. Association of the wild‐type (WT) trimer with catalytically inactive, but still substrate binding mutant trimer into hexameric chimera restores the high activity of the first trimer, characteristic of trimer incorporated in the hexamer of WT PPase. Interaction of PPase active sites suggests that there are pathways for information transmission between the active sites, providing the perfect organization and concerted functioning of the hexameric active sites in catalysis.

ENZYME ACTIVITY REGULATION BY AN OUTER PHYSICAL SIGNAL

The main principles and methods of creating artificial systems with the directional regulation of enzyme activity by an outer physical signal are discussed. We are presenting some experimental results for the systems working in the necessary regime and responding to light and temperature.

Bioelectrosynthesis as an alternative to photosynthesis

The CO2 reduction processes have been discussed as a way of designing an ecologically totally closed technology. An electric current and molecular hydrogen are the two related available agents that can be discussed as ecologically pure reductants. The most important products are liquid and gaseous fuels, the products of large-scale organic synthesis, monomers, and amino acids. For CO2 reduction, the necessary energy consumption and H2 costs were calculated. For complex organic molecules, amino acids for instance, the energy consumption does not make up the main portion of the costs.The biocatalytic systems of CO2 reduction based on cryoimmobilized cells are described. Conversion of CO2 into L-lysine with electrochemical decomposition of water was effected on the laboratory scale. A general unit for diverse technological processes can be a bioelectrosynthetic Index Entries: Bioelectrosynthesis; CO2 reduction; liquid fuels; amino acids; immobilized cells; economic estimates. modulus, an electrochemical hydrogen generator coupled with a biocatalytic converter of hydrogen and oxygen. The systems for bioelectrosynthesis of motor fuels and essential amino acids have been economically estimated and characterized. The possibilities of combining the solar energy transformation and H2–CO2 conversion have been discussed.

Kinetics of the dual-action mechanism of narcotic substances: conditions for conservative functioning of enzyme-receptor systems

We have studied the kinetics of the conservative behavior of systems which are subject to the dual action of an external effector or a negative feedback. Conditions have been found under which the dual-action mechanism produces conservative behavior. Negative feedback alone was shown not to produce the conservative behavior of an enzyme-receptor system.