Structural and Morphological Features of Anisotropic Chitosan Hydrogels Obtained by Ion-Induced Neutralization in a Triethanolamine Medium.

For the first time, anisotropic hydrogel material with a highly oriented structure was obtained by the chemical reaction of polymer-analogous transformation of chitosan glycolate-chitosan base using triethanolamine (TEA) as a neutralizing reagent. Tangential bands or concentric rings, depending on the reaction conditions, represent the structural anisotropy of the hydrogel. The formation kinetics and the ratio of the positions of these periodic structures are described by the Liesegang regularities.

STRENGTHENING SOCIETAL RESILIENCE DURING COVID-19 PANDEMIC.

Objective: The aim: To investigate factors that can negatively affect societal resilience in the context of the COVID-19 pandemic and identify communication aspects of strengthening resilience through information policy formation.

Patients And Methods: Materials and methods: In the research process, the authors employed the monographic and abstract-logical methods. The communication aspect analysis of strengthening social resilience in the context of the COVID-19 pandemic also grounded upon the results of the authors' sociological study "Motivation of compliance/non-compliance with quarantine restrictions by the population of Ukraine".

[Giant temporal bone cholesteatoma].

Presented clinical observation of a patient with exacerbation of left-sided chronic purulent otitis media complicated by extradural brain abscess, temporal bone osteomyelitis. The patient underwent a sanitizing operation on the left temporal bone with plastic closure of the defect in the postoperative cavity with a muscular-fascial flap. Described the postoperative management of the patient and presented the results of treatment 2 months after surgery.

Morphofunctional features of articular cartilage structure.

Background: Articular cartilage is highly-organized nonvascularized tissue which is responsible in humans for pressure absorption under load, as well as for the smoothness of the opposite tangential bone surfaces. The purpose of our research is to study structural and functional features of articular cartilage at light- optical level by using state-of-the-art research methods of bone-cartilage tissue.

Material And Methods: the study was conducted on samples of femoral heads.

Cases of the staff unaccounted exposure during the construction of the protective shell for a new confinement at the ChNPP site.

Objective: cytogenetic control of the staff radiation exposure level during the construction of the protective shell for a new confinement at the ChNPP site.

Materials And Methods: A cytogenetic examination was carried out for 32 staff persons from the contracting organ izations involved into construction of the protective shell for a new confinement. Additionally, for the goal of com parison, 28 persons who did not have professional contacts with the radiation factors were inspected.

[Enzymatic Synthesis of Acidic β-Lactams (Review)].

The currently known methods of enzymatic β-lactam synthesis, as well as the enzymes and heterogeneous biocatalysts used for this purpose, are presented, and the published reports on advances in the field of enzymatic synthesis of selected antibiotics belonging to the groups of acidic penicillins and acidic cephalosporins are summarized in the present review. The key conditions and parameters of biocatalytic processes, such as the biocatalyst form, concentration of the precursor compounds, solvent type, pH, temperature, etc. are analyzed and compared, and guidelines for further optimization of β-lactam synthesis are given.

Ionization constants and solubility of compounds involved in enzymatic synthesis of aminopenicillins and aminocephalosporins.

The article deals with experimental determination of ionization constants and solubility for the compounds (target products, initial β-lactams, acylating agents and by-products) involved in enzymatic synthesis of some therapeutically used aminopenicillins and aminocephalosporins, namely ampicillin, amoxicillin, cephalexin, cephadroxil, cephaloglycin, cefaclor, cefprozil, cefatrizine. Methodology of investigations and the evaluation of experimental data for the determination of ionization constants and solubility of the different type electrolytes are presented. Applications of the methods based on acid-base potentiometric titration and on determination of solubility-pH dependence of assayed substances are discussed.

[Enzymatic synthesis of beta-lactam antibiotics. Analytical review].

The paper presents an analytical review of the literature on enzymatic synthesis of semisynthetic beta-lactam antibiotics. The results of the studies on the thermodynamics and kinetics of beta-lactams synthesis are generalized and the approaches to increasing the efficiency of the biocatalytic processes based on both thermodynamically controlled synthesis (direct) and kinetically controlled synthesis (acyl transfer) are systematized. Characteristic features of the processes for separation of the reaction mass components and recovery of the final products of the biocatalytic synthesis of beta-lactam antibiotics are considered and the pathways to increasing the economic efficiency of biocatalytic processes used in design of the technologies and their introduction to manufacture are discussed.

[Novel beta-lactam structures: design problems].

The methology of the development of new biologically active betalactams is proposed. One of the two ways proposed is specific modification which is peculiar to certain betalactam structure and involves introduction of substitutes changing particular physico-chemical properties of the natural or synthetic analogous. General guidelines for modification of the biologically active compounds are given.

[Enzymatic synthesis of beta-lactam antibiotics. II. Aminocephalosporins].

Enzymatic synthesis of cephalexin and cefaclor with the use of immobilized aminocephalosporin synthetase from Xanthomonas sp. as a biocatalyst was studied. The employment of a mathematical model based on the acyl-enzyme mechanism of the biocatalyst action was shown possible for the quantitative description of the antibiotic syntheses.

[Enzymatic synthesis of beta-lactam antibiotics. I. Cefazolin].

Production of cefazolin by acyl transfer enzymatic synthesis with immobilised cefazolin synthetase from Escherichia coli as a biocatalyst acting in accordance with the mechanism including formation of the acyl-enzyme complex was shown possible. The process kinetic parameters and the ratio of the maximum conversion of the key amino acid and the initial concentrations of the substrate and nucleophile were determined. Correlation of the calculated and experimental data on the cefazolin yield in the enzymatic synthesis was good.

[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.

[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.

[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.

[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.