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S D Varfolomeev

Publications and source records attributed to S D Varfolomeev.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Reliability of elements and systems in enzymology.

The applications of the elements of reliability to the description of the stability and aging processes of enzymes and polyenzyme systems have been considered. The inactivation of individual enzymes or polyenzyme systems whose activity varies on the molecular level according to the "all-or-nothing" principle is described by an exponential reliability law. Systems of enzymes which are inactivated according to an exponential law have been considered. It has been shown that in the case of enzymes functioning in parallel, the value of the mean time of continuous operation is determined by the most stable enzyme, while in the case of sequentially functioning enzymes, this value is determined by the most labile. Systems whose aging process is related to the accumulation of "latent errors" and whose inactivation is characterized by gradual breakdowns are described by a normal reliability law. Systems with a combination of exponential and normal reliability laws have been considered. The use of a series of rigid quantitative criteria, such as the mean time for continuous functioning has been proposed for characterizing the stability of enzymes and polyenzyme systems. The theoretical points have been illustrated by experimental data on the stability of enzymes with hydrogenase activities, isolated chloroplasts, and cells of microscopic blue-green algae.

Enzymes↗
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[Replication protein RepN encoded by the RC plasmid of thermophilic bacterium Thermoanaerobacterium saccharolyticum: mutational analysis and deletion mapping of domains responsible for its lethal effect].

Amino acid sequence analysis of the product encoded by repN of Thermoanaerobacterium saccharolyticum (Clostridium thermosaccharolyticum) pNB2, which is capable of rolling-circle (RC) replication, revealed all known motifs conserved among replication (Rep) proteins that initiate RC replication of plasmids related to pC194/pUB110. Using the T7 expression system in Escherichia coli, RepN was identified as a 35K protein. Its lethal effect on bacterial cells was unusually high for a protein of the kind. Mutation analysis of the potential active centers (Y85F and Y211F) showed that the lethal effect of RepN is not associated with its putative topoisomerase (relaxase) activity. On evidence of deletion mapping, the lethal effect was attributed to the N- and C-terminal domains, each accounting for about 30% of the total protein. The RepN fragments essential for the lethal effect were found to share a motif, which showed no appreciable homology to known conserved motifs. The high lethal effect of RepN was assumed to result from duplication of the motif and to play an adaptive role, providing for the stable maintenance of the AT-rich plasmid in thermophilic bacterial cells.

Amino Acid Sequence↗
PubMedDate not supplied

[Characterization of urokinase type plasminogen activator modified by phenylglyoxal].

A chemical modification of single-chain urokinase-type plasminogen activator (scu-PA) with phenylglyoxal under mild conditions resulted in the scu-PA derivatives with various numbers of the modified Arg residues. The study of properties of the resulting derivatives demonstrated that the modification of 4-12 Arg residues did not cause any loss of the activator, fibrinolytic, and potential amidase activities of the activator. The scu-PA with four modified Arg residues was found to be the most stable derivative in human blood plasma; it causes a more efficient lysis of plasma clots than the native activator. Three of four modified Arg residues are supposed to be within the 178RRHRGGS184 cluster, which was localized in the superficial loop of the scu-PA globule and was shown to interact with the complementary series of negatively charged residues in the molecule of the main plasma inhibitor PAI-1. The neutralization of positively charged Arg residues in this cluster decreases the affinity of scu-PA and the double chain urokinase-type plasminogen activator for PAI-1, which results in an enhancement of the stability in plasma and the fibrinolytic efficiency of the activator. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2002, vol. 28, no. 4; see also http://www.maik.ru.

Arginine↗
PubMedDate not supplied

[Nucleotide sequence of the pNB2 plasmid from thermophilic bacteria Clostridium thermosaccharolyticum].

The complete nucleotide sequence of pNB2, a 1.9-kilobases cryptic plasmid from thermophilic Clostridium thermosaccharolyticum has been determined. The plasmid consists of 1882 base pairs and has a G+C composition of 27.2%. The sequence contains three open reading frames capable of coding for polypeptides two of which were identified in maxicell Escherichia coli extracts. Our future studies are directed toward a construction of pNB2-derivatives as vectors for Clostridia.

Amino Acid Sequence↗
PubMedDate not supplied

[Determination of minimal concentrations of biocorrosion inhibitors by a bioluminescence method in relation to bacteria, participating in biocorrosion].

By using a bioluminescence ATP assay, we have determined the minimal concentrations of some biocorrosion inhibitors (Katon, Khazar, VFIKS-82, Nitro-1, Kaspii-2, and Kaspii-4) suppressing most common microbial corrosion agents: Desulfovibrio desulfuricans, Desulfovibrio vulgaris, Pseudomonas putida, Pseudomonas fluorescens, and Acidithiobacillus ferrooxidans. The cell titers determined by the bioluminescence method, including not only dividing cells but also their dormant living counterparts, are two- to sixfold greater than the values determined microbiologically. It is shown that the bioluminescence method can be applied to determination of cell titers in samples of oil-field waters in the presence of iron ions (up to 260 mM) and iron sulfide (to 186 mg/l) and in the absence or presence of biocidal corrosion inhibitors.

Acidithiobacillus↗
PubMedDate not supplied

[Analysis of new opiate-like peptides using a radioreceptor method].

A screening of new synthetic opioid-like peptides has been carried out by the radioreceptor assay using selective labeled ligands to mu-, delta- and gamma-opioid receptors of the rat brain membranes. With this aim peptides from sequences of the following proteins were used: kapporphin-Tyr-Ser-Phe-Gly-Gly and its analogues-Tyr-Ser-Phe-Gly-Gly-NH2, Tyr-D-Ser-Phe-Gly-Gly, Tyr-D-Ser-Phe-Gly-Gly-NH2, myelorphin-Phe-Gly-Tyr-Gly-Gly, interenkephalin B-Arg-Arg-Gln-Phe-Lys and chimeric peptide IEPhBin 1-Tyr-Gly-Gly-Phe-Leu-Arg-Pro-Tyr-Ile-Leu consisting of leu-enkephalin and pentaneurotensin. It has been found that myelorphin has a prevalent affinity to mu-receptor, while the kapporphin analogues both to mu- and delta-receptors. The presence of pentaneurotensin in chimeric peptide does not affect the specificity of binding to opioid receptors, but decreases affinity to mu- and delta-receptors approximately by an order as compared to leu-enkephalin. Kapprorphin and interenkephalin B displace neither of the selective labeled opioid ligands under study.

Amino Acid Sequence↗
PubMedDate not supplied

[The use of photographic materials as a dry reagent for determining the peroxidase activity of biological preparations].

A new method is reviewed for measuring the peroxidase activity of biopreparations using light quantum-sensitized photographic material as a detector. The method involves the combination of the reactions of peroxidase oxidation of hydroquinone, a constituent part of the developing solutions, by hydrogen peroxide and photochemical interaction of the remaining hydroquinone with silver halogenides of the photoemulsion layer. Visually, up to 2 ng/ml of horse radish peroxidase is detectable. On photometry of the spots obtained, the limit of peroxidase demonstration amounts to 0.6 ng/ml. The data obtained during measurements of the peroxidase activity of the saliva, blood serum, plant extracts and immunoenzymic conjugates are provided.

Humans↗
PubMedDate not supplied

[Kinetics of reactions in polyenzyme systems. III. Electron transport processes].

Kinetic relationships of electron transport processes in biological systems have been analysed. Formal-kinetic description and discrimination of the two main models of electron transport processes in systems of homogeneously distributed carriers and in systems of structurally bound carriers is presented including steady-state and non-steady-state reaction kinetics. Methods of determination of limit-stage rate constant and rate constants for all elementary steps of the reaction are given. Dependencies of the degree of electron carriers reduction on donor and acceptor concentrations and the influence of reduction or oxidation of carriers on the kinetic properties of electron transport chain (electron influence factor) in the system of structurally-bound carriers have been analyzed. On the basis of kinetic models a molecular-kinetic interpretation of activation effect of mitochondrial respiratory chain during the process of electron transport is offered.

Cytochromes↗
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[The equation for platelet aggregation rate].

A platelet aggregation model in shear flow taking into account the kinetics of intercellular fibrinogen bond formation limited by aggregated platelets rotation time was considered. For this consideration the average duration of platelets interaction in flow with shear rate value G is shown to be pi/4G. One fibrinogen bond is sufficient to form a solid aggregate between two platelets. The equation for single platelets disappearance rate concerned with intercellular fibrinogen bond formation, stochastic character of bond distribution in collided platelets and hydrodynamically controlled interaction time was obtained. The Hill's approximation for the obtained aggregation rate dependences was suggested and appropriate constants were determined. The qualitative criterion of platelets aggregating systems behavior was introduced.

Humans↗
PubMedDate not supplied

[Stationary kinetics of catalysis by the hydrogenase of Thiocapsa roseopersicina].

Forward and reverse reactions of catalysis by a hydrogenase from T. roseopersicina in steady state have been investigated. The dependance of reaction rate on the concentration of substrates and of hydrogen ions has been studied. Detailed formal-kinetic analysis of possible mechanisms of enzyme action has been carried out and the classification of mechanisms of the reaction has been given. Comparison of experimental data with the equations obtained from formal-kinetic analysis has been undertaken and mechanisms compatible with experimental data were sorted out. Kinetic and molecular mechanism of the catalytic activity of hydrogenase has been proposed and elementary rate constants for the activation of molecular hydrogen have been calculated.

Catalysis↗
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[Determining the peroxidase level using tubular coal electrodes in flow-type systems].

An amperometric transducer with tubular coal electrodes has been worked out to determine the microquantity of peroxidase. The hydrodynamic parameters of the transducer were studied as were the relationship of the output signal to the concentration of the electroactive substance, the length of the electrode, the speed of the background electrolyte movement and the diffusion coefficient. The line section of the relationship between the strength of current and the peroxidase concentration is observed within the interval of the enzymic concentration 1-32 ng/ml with the exposure time of the enzymic reaction of 5-10 min.

Coal↗
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[Kinetic model of a multienzyme system of blood prostanoid synthesis. I. Mechanism of stabilization of thromboxane and prostacyclin levels].

A kinetic scheme of the prostacyclin-thromboxane system has been evolved on the basis of the authors experimental data and the results described elsewhere. The kinetic behavior of the model has been analysed with the aid of computer technology by varying the following parameters: phospholipase activities, free arachidonic acid exchange rates between platelets and endothelium, PGH-synthetase biosynthesis rates, velocities of arachidonic acid pathways other than the cyclooxygenase ones. It has been demonstrated that the biological system is capable of sustaining prostacyclin and thromboxane concentrations at steady fixed levels within a wide range of kinetic parameters.

Arachidonic Acid↗
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[Kinetic model of a multienzyme system of blood prostanoid synthesis. II. Dynamic responses to pharmacological agents--inhibitors of prostaglandin H synthetases].

The dynamic replies of the multienzyme system of blood prostanoid synthesis to the introduction of an irreversible inhibitor of prostaglandin H synthetase (PGH synthetase) have been analysed by using kinetic modelling. The alterations of arachidonic acid and PGH synthetase concentrations in platelets and endothelium and the concentrations of thromboxane and prostacyclin have been demonstrated. Particularities of kinetic behaviour of the system probably providing the therapeutic effect of non-steroidal anti-inflammatory drugs have been shown. Namely, the kinetic wave of free arachidonic acid and prostacyclin concentration with respect to thromboxane concentration appears after introduction of the drugs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

[2-component inhibition of prostaglandin H synthetase by nonsteroidal anti-inflammatory preparations].

A combined effect on the irreversible inhibitor aspirin and fast reversible inhibitors ibuprofen, naproxen and sodium salicylate on prostaglandin-H-synthetase was studied on microsomal fractions from ram vesicular glands. The fast reversible inhibitors were shown to bind to prostaglandin-H-synthetase at the same site as aspirin and thereby to protect the enzyme against irreversible inactivation by aspirin.

Animals↗
PubMedDate not supplied

[Kinetic model and mechanism of regulation of a multienzyme system of thromboxane synthesis].

A kinetic model has been suggested for the thromboxane synthesis polyenzyme system, taking into account the inactivation of a limiting enzyme, prostaglandin H-synthetase, in the course of the reaction. The model also includes the effect of phospholipase, adenylate cyclase, as well as the "outflows" of the components from the system, and basic regulatory effects in the system. A mathematical description of the model is given, and numerical solutions of the system of equations obtained for a wide variety of parameters. An analysis of the kinetic responses of the polyenzyme system shows that: 1) the system is highly conserved with respect to thromboxane concentration changes; 2) two cardinally different modes of the system are registered; they correspond to two insignificantly differing thromboxane steady-state levels; 3) transition of the system from one mode to the other is controlled by the phospholipase activity level which is sensitive to a change in the concentration of the regulator (cyclo-AMP or Ca ions) in the system. It is presumed that the two thromboxane steady-state levels are of physiological significance.

Arachidonic Acid↗