Search PubMed⌕ Search

Biomedical subjects

V I Iakovleva

Publications and source records attributed to V I Iakovleva.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[Resistance to heating and trypsin of glutamate dehydrogenase from liver mitochondria of frogs differing in thermotaxis].

The resistances to heat and trypsin hydrolysis served as indirect indices of conformational flexibility of glutamate dehydrogenase molecules. No difference in heat resistance was found between crystalline eletrophoretically homogeneous preparations of glutamate dehydrogenase from liver mitochondria of two species of frogs, the more southern Rana ridibunda and the more northern R. temporaria. However, glutamate dehydrogenase from R. ridibunda is digested by trypsin at a lower rate than that from R. temporaria, which may be explained by its lower conformational flexibility. Therefore positive correlation between conformational flexibility of glutamate dehydrogenase and mean ambient temperature of the species studied is revealed only with respect to resistance to proteolysis.

Animals↗
PubMedDate not supplied

[Synthesis of L-aspartic acid by Escherichia coli and Pseudomonas fluorescens as related to the cultivation conditions].

The capacity of the cultures Escherichia coli str. 85, 113, BC, C and K-12 and Pseudomonas fluorescens str. 1 to synthesize L-aspartic acid from fumarate and ammonium ions was studied. E. coli str. 85 was shown to synthesize the largest amounts of aspartic acid. The cultivation conditions which helped to increase the activity several times were selected. The product of fumarate amination by ammonium ions was identified and found to be L-isomer of aspartic acid with an angle of rotation of [alpha] 20/D = +25,5 degrees in 6 N HCl.

Aspartic Acid↗
PubMedDate not supplied

[Characteristics of morphological reactions in dog internal organs and endocrine glands during 6-year gamma irradiation].

Dogs were exposed to six-year gamma-irradiation with doses of 21-1140 rad/year; pathomorphological changes were studied in testicles thyroid gland, adrenals, liver and kidneys. The level of morphological changes in the organs during the six-year exposure was dissimilar and depended on the radiosensitivity of a specific organ, dose rate and acute irradiations that were applied during the experiment. In testicles morphological changes (reduction of layers of the spermatogenous epithelium, decrease of the number of spermatozoids in testicular canals) appeared during the first year of irradiation at a dose rate of 0.34 rad/day. Later, these changes progressed and by the end of the six-year exposure were followed by a distinct sclerosis of the interstitial tissue and hyperplasia of Leydig's cells. In the thyroid gland signs of the hypofunctional state were seen by the end of the second year of irradiation at a dose rate of 0.34 rad/day and persisted afterwards. In adrenals hypertrophy of the bundle and glomerular zones were observed during the second-fourth years of irradiation at a dose rate of 0.34 rad/day. As irradiation proceeded hyperplastic processes developed in the thyroid gland and adrenals (adenomatous nodes in the thyroid gland, adenomatous hyperplasia in the adrenal cortex). Vacuolar and fat dystrophy of hepatocytes and disturbed permeability of glomerular capillaries in the kidneys were detected only at the end of the third year of irradiation. During the fifth and, particularly, the sixth year of the exposure sclerotic changes in the liver vessels, hyalinosis of small arteries and nephrosclerotic foci in the kidneys were found.

Adrenal Glands↗
PubMedDate not supplied

[Stability of biocatalysts on the basis of carrageenan-immobilized Escherichia coli during continuous synthesis of L-malic acid].

Continuous enzymatic synthesis of L-malic acid from potassium fumarate in packed-bed flow reactors was investigated. Carrageenan-immobilized Escherichia coli cells were used as a biocatalyst. The operational stability of the biocatalyst fumarase activity was studied, and conditions for preserving high activity of the biocatalyst were determined.

Bacteriological Techniques↗
PubMedDate not supplied

[Determination of 3,4-dioxyphenyl-L-alanine by spectrophotometric and chromatographic methods in enzymatic synthesis using microbial cells].

A possibility of using the ninhydrin reaction for 3,4-dihydroxyphenyl-L-alanine (DOPA) determining during the synthesis from pyrocatechol and ammonium pyruvate was verified by using free and immobilized cells of Citrobacter freundii, st. 62. Spectrophotometric assay was performed at the adsorption maximum for the DOPA-ninhydrin complex at 390 nm. DOPA can be reliably quantified in the presence of all components at 20-fold and greater dilution of the reaction mixture. A high-sensitive quantitative assay of the reaction mixture was developed based on phase-reversed HPLC. A quantitative correlation was observed between spectrophotometric and chromatographic assays. The assays were employed to study in detail the initial period and equilibrium of DOPA synthesis and its characteristic features, which made it possible to construct a kinetic model of the process.

Catechols↗
PubMedDate not supplied

[Isolation of spheroplasts from Escherichia coli 85 for aspartate-ammonia-lyase localization].

Conditions were determined for preparation of spheroplasts from E. coli under the action of lysozyme in the presence of EDTA. The preparation took from 10 to 15 min. The degree of conversion to spheroplasts was monitored spectrophotometrically at 660 nm. The spheroplasts formed were unstable in Tris-HCl buffer and immediately lysed, but they were more stable in 1 M sucrose. At lysozyme concentrations above 40 micrograms/ml of the reaction mixture, the cells lysed to a greater extent. The distribution of aspartate ammonia-lyase activity between the precipitate of the spheroplasts and the supernatant allowed the authors to suggest that aspartase should be located in the cytoplasm.

Ammonia-Lyases↗
PubMedDate not supplied

[Kinetic study of 3,4-dihydroxyphenyl-L-alanine synthesis in Citrobacter freundii cells immobilized in carrageenan].

A kinetic study was carried out of the enzymatic synthesis of 3,4-dihydroxyphenyl-L-alanine (DOPA) by the Citrobacter freundii 62 cells, possessing tyrosine-phenol-lyase (TPL) activity, immobilized in carrageenan, and optimum conditions of the reaction were found. The dependence of the TPL activity and its stability on the conditions of the DOPA synthesis was investigated. The TPL activity was higher and more stable in the immobilized cells as compared to free ones.

Bacteriological Techniques↗
PubMedDate not supplied

[Enzymatic synthesis of L-malic acid from fumaric acid using immobilized Escherichia coli cells].

Optimal conditions were chosen for cultivation of Escherichia coli 85 cells with a rather high fumarate-hydratase activity on a cheap medium containing no edible raw material. An active biocatalyst for the synthesis of L-malic acid from fumaric acid was obtained based on E. coli 85 cells immobilized in carrageenan. The enzymatic synthesis of L-malic acid from potassium fumarate was kinetically studied and optimized. Some thermodynamic parameters of fumaric acid hydration into malic acid were determined. A technique for assaying the reaction mixture was developed that involved high performance liquid chromatography.

Escherichia coli↗
PubMedDate not supplied

[Aspartate aminotransferase activity of different strains of Escherichia coli].

Aspartate-aminotransferase activity was measured in strains of Escherichia coli grown no meat infusion broth. As an enzyme cells with damaged permeability of the cytoplasmatic membrane were used. The cells were damaged by an addition of toluene at a concentration of 1% of the reaction mixture by volume. These cells showed 50--60% aspartate-aminotransferase activity as compared with aliquotes of the cell-free extract. E. coli synthesized oxalacetic and glutamic acids from L-aspartic acid and alpha-ketoglutaric acid. Glutamic acid was identified by thin-layer chromatography on Fixion plates. E. coli str. 85 cells and their extracts grown on the synthetic medium containing glucose or glycerol showed a two-fold specific aspartate-aminotransferase activity as compared with those cultivated on meat-infusion broth.

Aspartate Aminotransferases↗
PubMedDate not supplied

[L-asparatic acid synthesis from ammonium fumarate by free and immobilized Escherichia coli cells].

E. coli 85 cells with a high aspartate-ammonia-lyase activity were immobilized through polyacrylamide gel incorporation. Proper conditions to assay aspartase activity of E. coli cells were developed. Kinetic patterns of aspartate-ammonia-lyase reaction catalyzed by free and immobilized E. coli 85 cells were studied. The synthesis of L-aspartic acid from ammonium fumarate had the following characteristics: specific activity of (4--6) . 10(-5) mmole/mg.sec for free cells and (6--8) . 10(-5) mmole/mg.sec for immobilized cells with their content in polyacrylamide gel of 5--10 mg protein per g wet gelm pH 8.3--10.0.

Aspartic Acid↗
PubMedDate not supplied

[Comparison of the aspartase activity and its stability in Escherichia coli cells immobilized on polyacrylamide gel and carrageenan].

The conditions for immobilization of Escherichia coli cells (Soviet strain 85) on the natural polysaccharide carrier carrageenan (Soviet-made) were investigated and kinetic regularities of the aspartase reaction catalysed by immobilized in carrageenan cells of E. coli 85 were established. The conditions for retaining a high aspartase activity and stability of biocatalysts based on the E. coli 85 cells immobilized in PAAG and carrageenan were determined using full-loaded tanks for continuous synthesis of L-aspartic acid. The time-stable aspartase activity of the biocatalyst can be increased by treating the beads of the catalyst with bifunctional reagents (hexamethylenediamine, glutaraldehyde), the most active catalyst for the biotechnological synthesis of L-aspartic acid being obtained when carrageenan is used.

Acrylic Resins↗
PubMedDate not supplied

[Aspartase activity and the stability of Escherichia coli cells immobilized in different carrageenan samples].

The cells of Escherichia coli 85 immobilized in carrageenan from various sources were being studied for the aspartase activity and stability. These properties of the resultant preparations which display a relatively high and stable biocatalytic activity were shown to be almost independent of the raw material from which carrageenan was obtained and of the degree of its purification.

Acrylic Resins↗