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M V Ivanov

Publications and source records attributed to M V Ivanov.

At least 19 recordsLinked to original sources
PubMed1991

Engineering of functional supramacromolecular complexes of proteins (enzymes) using reversed micelles as matrix microreactors.

The size of the inner water cavity of reversed micelles formed in a triple system 'water-surfactant-organic solvent' can be widely varied by changing the degree of surfactant hydration. This gives grounds to use reversed micelles as matrix microreactors for the design of supramolecular complexes of proteins. Using ultracentrifugation analysis, it has been demonstrated that the oligomeric composition of various enzymes (ketoglutarate dehydrogenase, alkaline phosphatase, lactic dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase) solubilized in reversed micelles of Aerosol OT [sodium bis(2-ethylehexyl)sulfosuccinate] in octane changes upon variation of the degree of hydration. An oligomeric complex forms under conditions when the radius of the micelle inner cavity is big enough to incorporate this complex as a whole. At lower degrees of hydration the micelles 'uncouple' such complexes to their components. The catalytic properties of various oligomeric complexes have been studied. Possibilities of using reversed micelles for the separation of subunits of oligomeric enzymes under non-denaturating conditions have been demonstrated. In particular, the isolated subunits of alkaline phosphatase, lactic dehydrogenase and glyceraldehyde-3-phosphate have been found to be active in Aerosol OT reversed micelles. The dependences of the catalytic activity of oligomeric enzymes represent saw-like curves. The maxima of the catalytic activity observed at these curves relate to the functioning of various oligomeric forms of an enzyme. The radii of the micelle inner cavity under conditions when these maxima are observed correlate with the linear dimensions of the enzyme oligomeric forms. Correlation of the position of a maximum with the shape of an oligomeric complex is discussed.

Alkaline Phosphatase↗
PubMed1987

[Detection of ligand-induced conformation changes in lactate dehydrogenase by using fluorescent probes].

The binding of ANS to apolactate dehydrogenase (apo-LDH) is accompanied by a 300-fold increase in dye fluorescence with a shift of the emission maximum from 515 to 479 nm, as well as by quenching of intrinsic protein fluorescence. A tetrameric LDH molecule has 6.4 +/- 1.6 non-interacting dye-binding sites with an association constant equal to (4.3 +/- 1.6) X 10(3) M-1. NAD+ added at saturating concentrations does not alter the number of ANS binding sites or the association constant value. The formation of binary LDH.NAD+, LDH.NADH, LDH.AMP and LDH.pyruvate complexes causes the quenching of fluorescence of the enzyme-bound ANS. The extent of quenching observed at ligand saturating concentrations differs for each ligand. Pyruvate added to the binary LDH.AMP complex exerts no effect on the fluorescence of protein-bound ANS; this indicates that the binding of AMP causes some alterations in the microenvironment of the substrate-binding site. Nicotinamide mononucleotide (NMN) can act as a coenzyme in the LDH-catalyzed reaction. AMP added together with NMN displays an inhibitory effect. The cationic (auramine O) and anionic (ANS) fluorescent probes bound to LDH exhibit different responses to conformational changes accompanying the transition from the apoenzyme to the LDH X NAD-pyruvate complex.

Anilino Naphthalenesulfonates↗
PubMed1987

[Relation between the thermostability of the tetrameric molecule of lactate dehydrogenase from swine muscles and the degree of occupancy of its active sites with ligands].

Using differential scanning microcalorimetry and measurements of protein fluorescence, the thermal denaturation of lactate dehydrogenase (LDH) from porcine muscle (in the apo-form as well as in the form of the enzyme-pyruvate, enzyme-NAD+ and enzyme-NAD-pyruvate-adduct complexes) was studied. Pyruvate binding did not affect the thermal stability of LDH. NAD+ exerted a stabilizing effect on the enzyme, the value of which was proportional to the number of ligand molecules bound per LDH tetramer. The formation of the abortive LDH-NAD-pyruvate complex in one, two or three active centers of the enzyme tetramer did not influence the values of calorimetric parameters of thermal denaturation in comparison with those for the apoenzyme. The occupancy of all four active centers of LDH by the adduct resulted in a sharp increase of the enzyme thermal stability and tightness of the LDH adduct complex as compared with complexes formed upon partial saturation. The experimental results are suggestive of the existence of a concerted conformational transition of the LDH tetramer induced by the formation of the LDH-NAD-pyruvate complex in the last active center of the tetramer.

Animals↗
PubMed1986

[Comparative study of glyceraldehyde-3-phosphate dehydrogenases isolated from rabbit skeletal muscles and baker's yeast using cationic fluorescent probes].

The tetrameric molecule of glyceraldehyde-3-phosphate dehydrogenase possesses the ability to bind fluorescent probes of cationic nature (auramine O and acridine orange) outside the active center. The rabbit skeletal muscle and yeast enzymes share some common features, e.g., the conformational non-equivalency of subunits; two subunits per tetramer can bind auramine O; conformational changes caused by the binding of adenyl mononucleotides and involving the microenvironment of auramine O binding sites; the ability to bind the cationic probe at pH values typical for the maximal activity of the enzyme in the reaction of glyceraldehyde 3-phosphate oxidation. The yeast and rabbit muscle enzymes are distinguished in terms of localization of the probe binding sites with respect to the active center and/or in the nature of conformational changes induced by NAD+ binding. It was demonstrated that nicotinamide mononucleotide may serve as a co-enzyme in glyceraldehyde 3-phosphate oxidation catalyzed by yeast dehydrogenase; this reaction in inhibited by AMP.

Acridine Orange↗
PubMed1977

[Use of a fluorescent probe for the study of the active center of D-glyceraldehyde-3-phosphate dehydrogenase].

The effect of NAD on the binding of 1-anilino-8-naphthalene sulfonate (ANS) to yeast glyceraldehyde-3-phosphate dehydrogenase has been studied using difference spectrophotometric and fluorescence techniques. Coenzyme addition causes the displacement of ANS from its complex with the dehydrogenase, as suggested by the effect of NAD on the fluorescence of the enzyme--ANS complex, as well as on the magnitude of the difference spectrum of the complex. Adenine containing NAD fragments, adenosine, 5'-AMP, and ADP were shown to compete with ANS for the common site on the enzyme using fluorimetric technique; in the case of adenosine and 5'-AMP a direct method of analytical ultracentrifugation was also employed. The results obtained by both methods suggest the dye binding at the adenine subsite of the dehydrogenase. The interaction with ANS causes no detectable conformational changes of the protein. The fluorescence of the dye-enzyme complex increases and the emission maximum shifts to shorter wavelengths on addition of nicotinamide mononucleotide. This suggest some conformational changes to occur in the microenvironment of the bound dye in response to the interaction with the ligand in the nicotinamide subsite. The participation of the nicotinamide subsite of the active center in determining the character of conformational transitions associated with coenzyme binding to glyceraldehyde-3-phosphate dehydrogenase is discussed.

Adenine Nucleotides↗
PubMedDate not supplied

[Fractionation of sulfur isotopes by phototrophic sulfur bacterium Ectothiorhodospira shaposhnikovii].

Two processes of sulphur isotope fractionation have been found in experiments with the sulphur purple bacterium Ectothiorhodospira shaposhnikovii. As a result, a light isotope, 32S, is concentrated in residual hydrogen sulphide, and a heavy isotope, 34S, in elementary suphur which is deposited outside the cell. The sulphate produced is lighter than elementary sulphur. Fractionation of sulphur isotopes is observed in natural conditions and is confined to places of mass growth of photosynthetic sulphur bacteria.

Chemical Fractionation↗
PubMedDate not supplied

[Fractionation of stable sulfur isotopes during microbiological processes in Slavyansk lakes].

The isotopic content of sulphur in sulphates increases with depth in waters containing hydrogen sulphide of the meromictic lakes Repnoe and Veisovo as a result of microbiological reduction of sulphates. At the same time, hydrogen sulphide enrichments 19 to 25% of the light isotope 32S in the lake Veisovo, and 24 to 32% in the lake Repnoe. The fractionation of sulphur isotopes, manifested in the enrichment of sulphides with lighter isotopes, and that of sulphates with heavier isotopes, was found also in the bottom deposits of the lake Repnoe. The isotope and microbiological data suggest that, in the zone of mass growth of the phototrophic sulphur bacteria in the lake Repnoe, there are two processes of fractionation: (a) due to the bacterial reduction of sulphates; and (b) due to anaerobic oxidation of hydrogen sulphide, resulting in the enrichment of hydrogen sulphide with the light isotope 32S by 5 to 7 promille.

Bacteria↗
PubMedDate not supplied

[Radioisotope method of determining the intensity of bacterial methane formation].

The rate of methane formation by bacteria was determined by the isotope tracer technique using labeled carbon in the form of bicarbonate. The rate of methane production in the ooze deposits of the Kuznechikha lake was calculated by this technique to constitute 7.46 to 7.70 cm3 CH4 per 1 litre per day. The rate of the process was shown to depend on the number of methane-producing bacteria.

Bacteria↗
PubMedDate not supplied

[Determination of the rate of microbiological oxidation of methane using 14CH4].

The rate of microbiological oxidation of methane was determined by a technique using 12CH4. About 75-96 percent of the carbon form the methane oxidized by microorganisms was found in carbon dioxide, the remaining part was incorporated into the microbial cells. The rate of microbiological mehtane oxidation in the water of the Mari lakes was 6.4 times 10(-3) to 464.4 times 10(-3) cm3 CH4/litre per day.

Bacteria↗
PubMedDate not supplied

[Intensity of bacterial methane formation in ooze deposits in lakes].

The rate of methane production of bacteria via the decomposition of acetate in ooze deposits of the Mari lakes was 0.0165 to 0.483 mg CH4/day/ litre wet ooze. From 32 to 98 per cent of methane in the ooze of studied reservoirs formed through microbiological reduction of carbon dioxide by hydrogen.

Acetates↗