Molecular cloning, isolation, and properties of chaperone Skp from Yersinia pseudotuberculosis

The skp gene of Yersinia pseudotuberculosis was expressed without its signal sequence in Escherichia coli BL21(DE3) cells. The recombinant protein Skp accumulated in soluble form in the cytoplasm of the producer strain. The protein was isolated and characterized: the molecular weight, isoelectric point, N-terminal amino acid sequence (20 amino acid residues), and the content of the secondary structure elements were determined. Using cross-linking stabilization and high-mass MALDI-TOF mass spectrometric analysis, it was found that rSkp forms a stable homotrimer in solution and interacts with human IgG. Three-dimensional models of the Skp trimer and its complexes with Fc- and Fab-fragments of human IgG1 were constructed by computer modeling.     

Isolation and characterization of recombinant OmpF-like porin from the Yersinia pseudotuberculosis outer membrane

The encoding sequence of the pore-forming OmpF-like protein from the Yersinia pseudotuberculosis outer membrane was cloned and expressed in Escherichia coli cells. Conditions for isolation and refolding of recombinant monomer and porin trimer were selected. Their spatial structures were characterized by the intrinsic protein fluorescence and CD spectroscopy. It was shown that recombinant porins are similar in the composition of secondary structure elements to isolated porins, but have a considerably less compact tertiary structure. The pore-forming activities of the recombinant proteins are similar to those of Y. pseudotuberculosis native porins.     

New chitosan derivatives with potential antimicrobial activity

A series of four water-soluble chitosan derivatives differing in molecular mass, hydrophobicity, and charge was synthesized and tested for the intensity of their effects on Gram-negative and Gram-positive bacteria. It was shown that the tested compounds allowed the penetration of ethidium bromide into the bacteria, which showed increased permeability of their cell walls under the effect of chitosans. The tolerance to various chitosan derivatives differed in Gram-negative and Gram-positive bacteria. The Gram-negative bacteria were the most responsive to high-molecular chitosan and the Gram-positive ones, to N-,O-carboxypropylchitosan, whereas high-molecular chitosan had little effect. Research on the correlation between the structure and activity of the studied compounds revealed that depolymerization of chitosan reduced, and introduction of hydrophobic substantives in chitosan molecule significantly enhanced its permeability effect on bacterial cell walls. The obtained results provide a basis for the construction of new chitosan derivatives with antimicrobial activities.     

Numerical simulation of a surface barrier discharge in air

The development of a surface barrier discharge in air at atmospheric pressure under the action of a constant voltage of different polarity is simulated numerically. When the polarity of the high-voltage electrode is negative, the discharge develops as an ionization wave that moves along the dielectric surface. When the polarity is positive, the discharge develops as a streamer that first moves above the dielectric surface and then comes into contact with and continues to develop along it. In the case of a high-voltage electrode of positive polarity, the discharge zone above the dielectric surface is approximately five times thicker than that in the case of negative polarity. The characteristic aspects of numerical simulation of the streamer phase of a surface barrier discharge are discussed. The numerical results on the density of the charge stored at the dielectric surface and on the length of the discharge zone agree with the experimental data.     

Instability of chromosomes in human nerve cells (Normal and with Neuromental Diseases)

It is assumed that the genetic mechanism of pathogenesis of such widely spread neural and mental diseases as schizophrenia (SZ), autism, ataxia-telangiectasia (AT), and Alzheimer’s disease (AD) is associated with structural and functional genomi biological markers of genomic instability. The currently available methods of molecular cytogenetics (I-MFISH, QFISH, and ICS-MCB) facilitate the solution of numerous fundamental biological problems, including analysis of genomic variations in brain cells. Using these methods, we have studied for the first time aneuploidy in human embryo and adult brain cells (normal and with AT, AD, and SZ) as well as in blood cells of children with autism. The level of aneuploidy was increased two- to threefold in the embryo brain with a subsequent reduction of the number of abnormal cells in the adult brain. In the case of SZ, mosaic aneuploidy for chromosomes 1, 18, and X was found. The study of blood cells from children with autism showed chromosomal mosaicism for chromosomes X, 9, and 15. In the case of AT, we observed a global expression of aneuploidy in up to 20–50% of cortex and cerebellum neurons. In addition, a local instability of chromosome 14 was revealed in the degenerating cerebellum in the form of breaks in the 14q12 region. In the case of AD, a tenfold increase was observed in the level of aneuploidy for chromosome 21 in brain sections subjected to neurodegeneration. These data indicate that mosaic genomic instability in nerve cells is one of the mechanism of neurodegenerative and mental diseases.     

The effect of a single dose of arecholine and atropine administration on activities of carboxypeptidase H and phenylmethylsulfonyl fluoride-inhibited carboxypeptidase in the nervous system of rats

The effect of a single dose of arecholine and atropine administration on the activities of carboxypeptidase H and phenylmethylsulfonyl fluoride-inhibited carboxypeptidase involved into the final stage of formation of biologically active neuropeptides from precursors has been studied in brain and adrenals. Changes in the enzyme activities were evident during at least 72 h after administration of these drugs to rats. These results suggest that the decrease in the activity of these enzymes may represent one of possible mechanisms involved into reduction of neuropeptide levels during inhibition and activation of cholinergic system.     

On the possibility of the electron-hole plasma conductivity in diamond being negative

The mobilities of charge carriers in boron-doped diamond at low temperatures are estimated by numerically solving the Boltzmann equation for a steady-state nonequilibrium velocity distribution function of the carriers with allowance for their scattering by phonons. Estimates show that, at temperatures of up to 100 K, charge carriers with a negative mobility exist over a fairly broad (on the order of 100 K) range of their energies. In the steady-state case, the absolute mobility integrated over the distribution function turns out to be positive, but there are grounds to suppose that, in the case of an unsteady pulsed source of charge carriers, it may become negative.     

Low molecular weight derivatives of different carrageenan types and their antiviral activity

A number of low molecular weight (LMW) fractions of carrageenans with different structural types were obtained by free radical depolymerization (H₂O₂), mild acid hydrolysis (HCl), and a specific enzyme. Three samples of carrageenans were depolymerized: kappa-carrageenan from Chondrus armatus, kappa-carrageenan from Kappaphycus alvarezii, and kappa/beta-carrageenan from Tichocarpus crinitus with initial molecular weights of 250, 390, and 400 kDa, respectively. The chemical depolymerization by two methods resulted to LMW derivatives of carrageenans with molecular weight from 1.2 to 3.5 kDa. Oligosaccharides of kappa- and kappa/beta-carrageenans with molecular weight of 2.2 and 4.3 kDa, respectively, were obtained after enzymatic depolymerization by recombinant kappa-carrageenase from Pseudoalteromonas carrageenovora. It was shown that the antiviral activity of high molecular weight carrageenans against tobacco mosaic virus was higher than that of their LWM derivatives independently on the depolymerization method. The method of depolymerization had some influence on the antiviral activity of carrageenan. LMW derivatives of kappa- and kappa/beta-carrageenans obtained by mild acid hydrolysis showed higher antiviral activity than the products of free radical depolymerization. The oligosaccharides prepared by enzymatic degradation possessed the lowest activity.