Novel Chromogenic Substrate for Bacterial β-Lactamases Based on Cephalosporin Modified with an Epoxy Group

Beta-lactamases are the key enzymes involved in resistance to beta-lactam antibiotics in pathogenic bacteria causing infectious diseases. The search for new inhibitors and the study of the resistance mechanisms require the production of chromogenic substrates for beta-lactamases. A novel cephalosporin derivative with an epoxy functional group named CMPD1 is synthesized. It is shown to be a substrate for TEM type beta-lactamases, which is hydrolyzed to form a colored product. The hydrolysis product has an optical absorption maximum at 450 nm. The difference in the absorption maxima of the substrate and the product is 95 nm, and, therefore, CMPD1 exceeds the previously described substrates, according to this parameter. It has been found that the CMPD1 compound is hydrolyzed only by the TEM type beta-lactamases that lack mutations in the active site. This can be used to study the mechanisms of the catalytic effect of beta-lactamases.     

Synthesis and Antimicrobial Activity of 5-(Het)aryl-3-hydroxy-1-hydroxyethyl-4-(thienyl-2-carbonyl)-3-pyrrolin-2-ones

Russian Journal of General Chemistry - A series of novel 5-(het)aryl-3-hydroxy-1-hydroxyethyl-4-(thienyl-2-carbonyl)-3-pyrrolin-2-ones was synthesized by reacting methyl thienyl-2-carbonylpyruvate...     

Specific features of the polarization of thin water films in the field of the active surface of a mica crystal

The dependence of the permittivity of thin water films on their thickness in the field of the active surface of a mica crystal was investigated experimentally and theoretically. A model of the interaction between polar water molecules and the electric field of the crystal surface was considered within the framework of the Kirkwood theory. A comparison of the results of the theoretical calculations with the experimental data made it possible to determine the characteristics of the electric field of the crystal surface and demonstrated that the proposed model adequately describes the main features revealed in the polarization of the thin water films.     

Study of narrow resonances of coherent radiation in time separated fields in SF6

The present paper reports for the first time application of coherent radiation in time separated fields (CRTSF) for high resolution spectroscopy in gases. Experimentally the high resolution spectrum of SF₆ has been obtained by the time delay averaging of the CRTSF signals.     

Study of catalytic properties of recombinant β-lactamases TEM-1 and TEM-171 of the molecular class A

Homogeneous preparations of recombinant β-lactamases TEM-1 and TEM-171 of molecular class A, differing by an amino acid substitution of valine at position 84 to isoleucine (Val84Ile), was obtained. The kinetic parameters of the β-lactamase TEM-171 were determined using a chromogenic substrate CENTA (K _{M eff} = 23 μM, K _cat = 102 s^–1). The competitive inhibition of recombinant β-lactamases TEM-1 and TEM-171 by tazobactam was ascertained. The values of the inhibition constants in the hydrolysis of the CENTA substrate amount to 0.057 and 0.047 μM for TEM-1 and TEM-171, respectively. It was shown that the Val84Ile mutation leads to a decrease of TEM-171 enzyme thermal stability by 1.5 times.     

Synthesis and biological activity of fluorine-containing amino derivatives based on 4-caranethiol

Fluorine-containing N-substituted sulfinamides were synthesized via 4-caranethiol-based sulfenimines and sulfinimines. Stereochemical features of oxidation of sulfenimines and addition of fluorine-containing reagents to sulfinimines were discussed. Antimicrobial activities of the obtained compounds were screened.     

Heat release kinetics in the reaction of decane with nitric acid

The kinetics of the reaction of decane with nitric acid (25.07–75.53 %) at 57.8 to 119 °C in an acid-decane-gas triphasic system was studied. The main contribution to the rate of heat release is made by the oxidation of decane with nitrogen dioxide in the organic phase proceedingvia the mechanism of a degenerate branched-chain reaction. Nitration plays the role of a chain termination reaction. The acid phase is the source of NO₂, whose content increases with oxidation. The equilibrium of the nitrogen dioxide distribution in the triphasic system was analyzed. The kinetic law of the reaction, the dependences of the reaction constants of the initial and catalytic stages on temperature and the acid phase composition were determined. The results allow one to calculate the rate of heat release in the decane-HNO₃ system under any conditions of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1986–1991, August, 1996.