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Biomedical subjects

G S Libinson

Publications and source records attributed to G S Libinson.

18 recordsLinked to original sources
PubMed1995

[Kinetics of 7-aminocephalosporanic acid in aqueous solutions].

Stability of 7-aminocephalosporanic acid (7-ACA) and desacetyl-7-ACA in aqueous solutions at the pH value higher than 6 and wide ranges of the temperature was studied. The kinetic parameters of the hydrolysis of the ester link in the molecule of 7-ACA and the openings of the betalactam link in the molecules of 7-ACA and desacetyl-7-ACA were estimated. It was shown that all the destruction processes were describable by the 1st order equations. A procedure for the calculation of the velocity constants of the above mentioned three processes by changes in the concentration of 7-ACA and desacetyl-7-ACA in the solutions is described.

Biotransformation↗
PubMed1994

[Stability of various cephalosporins in solutions. Cefazolin, cefazedone, cefaclor].

The kinetics of splitting out the substitute at C3 in the molecule of beta-lactam antibiotics such as cefazolin, cefaclor, cefazedone and others as well as that of splitting out the chlorine atom in the side radical of the cefazedone molecule was studied within wide ranges of pH and temperature. The destruction processes for all the investigated compounds were shown to be described by the 1st order equations. The values of the activation energy, pre-exponential factors and reaction order by the hydrogen ions were measured. This provided the mathematical description of the destruction processes within wide ranges of pH and temperature. An unusual mechanism of synchronous splitting out the substitute at C3 and one of the chlorine atoms in the side radical of the cefazedone molecule was observed.

Anti-Infective Agents, Urinary↗
PubMed1988

[Calculation of a single and of subsequent extraction-reextraction cycles].

Estimation of the equilibrium distribution in the organic solvent-water system provided analysis of efficiency and optimal arrangement of subsequent extraction-reextraction cycles in isolation of various compounds. The analysis was performed with respect to optimization of the total yield and required volumes of the intermediate phases. It was shown that the best arrangement of the subsequent extraction-reextraction cycles depended on the compound distribution coefficients at various stages.

Chemistry Techniques, Analytical↗
PubMed1987

[Benzylpenicillin interaction with amines in the organic phase].

Benzylpenicillin interaction with amines in the nonaqueous phase was studied by pH dependence of the coefficient of the antibiotic distribution in the system of amine butyl acetate solution--water. A distribution scheme involving interaction of the amine molecular and cationic forms with benzylpenicillin and amine dissociation equilibrium in organic solution is described. On the basis of the experimental data the interaction and dissociation constants were determined for a number of aromatic and aliphatic amines.

Amines↗
PubMed1981

[Distribution of carbenicillin, benzylpenicillin and phenylmalonic acid in an organic solvent-water system].

Distribution of carbenicillin, benzylpenicillin and phenylmalonic acid in butyl acetate-water and methylene chloride-water systems within wide ranges of pH of the aqueous phase was studied. The experimental data were reviewed taking into account the distribution between the phases of the compound molecules and dissociation of the acids in the aqueous solution. The distribution constants of the compound molecules were calculated to be 37 (the literature data), 11.6 and 5.2 for every antibiotic respectively in the first system and 10 and 0.24 for carbenicillin and benzylpenicillin in the second system (the value for phenylmalonic acid was not calculated). When the concentration of carbenicillin in butyl acetate is high, dimerization of the acid molecule in the nonaqueous phase should be taken into the account. The dimerization constant is equal to 16.6 M-1.

Carbenicillin↗
PubMed1981

[Sisomicin. The mechanism of admixture inactivation and formation].

Inactivation of sisomicin in aqueous solutions was studied under various conditions. At pH 4-10 and a temperature of 60 degrees C the inactivation rate constant was equal to (5-10) X 10(-5) hour-1 and remained stable. At lower pH values the inactivation rate constant increased: 5.5 10(-3) (60 degrees C) at pH 0.5. The activation energy of the inactivation reaction was 27 (pH 0.5) and 32 (pH 4.0) kcal/mol. The study on the behaviour of sisomicin in solutions with different pH values under the environmental conditions and in the atmosphere of nitrogen showed that at low pH values the inactivation was mainly determined by hydrolysis of the glycoside bond. Formation of coloured compounds did not include the oxidation reaction. At pH about 7.0 oxidation of the antibiotic or of the products of its degradation with respect to the double bond played a significant role in the inactivation and formation of the coloured substances.

Disaccharides↗
PubMed1980

[Cephalosporin C stability in aqueous solutions].

Stability of cephalosporin C in aqueous solutions at various temperatures was studied. The kinetic parameters of the inactivation process providing estimation of the inactivation rate constant of cephalosporin C at pH 0-12.5 and various temperatures were evaluated. It was found that the zinc ions had no specific effect on the inactivation rate.

Buffers↗
PubMed1980

[Determination of the sulfate ion content in antibiotic sulfate salts by a complexometric titration method].

A possibility of assaying antibiotic sulfates, such as gentamicin, kanamycin, monomycin, neomycin, ristomycin, streptomycin, florimycin and polymyxin M sulfates for sulfate ions by titration with barium chloride in the presence of chlorphosphonaso-III, a metal indicator immediately in the salt solutions or after elimination of the cation by means of ion exchange (sulfocation exchange resins in H+-form) was tested. The procedure was shown to be adequate to the classical weight method.

Anti-Bacterial Agents↗
PubMed1976

[Relationship between the magnitude of Km and pH for L-asparaginase].

The dependency of L-asparagine hydrolysis rate on L-asparagine concentration in the presence of L-asparaginases from E. coli and Erw. carotovora is studied in a broad pH range. Km values are calculated from the data obtained. It is found that Km insignificantly depends on pH value with the pH range of 5-9 for both asparaginases. Sharp Km maximum is observed at pH greater than 9 in both cases. The maximum position does not coinside with enzyme isoelectric points and with the region of the substrate transition from zwitterionic form into anionic one.

Asparaginase↗
PubMedDate not supplied

[Physicochemical aspects of the mechanism of the mineralization of epiphyseal cartilage in enchondral osteogenesis].

Mechanism of epiphysial cartliage mineralization is considered in terms of ion exchange concepts. Chondroitin-sulfate of matrix, which is a polyelectrolyte, served as a donor od calcium ions. Pericellular zone of matrix is considered as a semipermeable membrane. The energetic basis of the process is provided by interacellular glycogenolysis in chondrocytes, entering the zone of mineralization. High concentration of glucose in lacunas of chondrocytes led to osmotic transport of water from matrix to lacunas, causing an increase in concentration of ions in free volume of the matrix. Due to ion exchange release of calcium ions occurred from the phase of polyelectrolyte into the free volume, where the state of saturation was achieved and dicalcium phosphate CaHPO4 was precipitated. Stereologic studies of epiphysial cartilage, simulation experiments and calculations corroborate the mechanism of mineralization advanced.

Bone Matrix↗