Discrimination between perfect and mismatched duplexes with oligonucleotide gel microchips: role of thermodynamic and kinetic effects during hybridization

The efficiency of discrimination between perfect and mismatched duplexes during hybridization on microchips depends on the concentrations of target DNA in solution and immobilized probes, buffer composition, and temperature of hybridization and is determined by both thermodynamic relationships and hybridization kinetics. In this work, optimal conditions of discrimination were studied using hybridization of fluorescently labeled target DNA with custom-made gel-based oligonucleotide microchips. The higher the concentration of immobilized probes and the higher the association constant, the higher the concentration of the formed duplexes and the stronger the corresponding fluorescence signal, but, simultaneously, the longer the time needed to reach equilibrium. Since mismatched duplexes hybridize faster than their perfect counterparts, perfect-to-mismatch signal ratio is lower in transient regime, and short hybridization times may hamper the detection of mutations. The saturation time can be shortened by decreasing the probe concentration or augmenting the gel porosity. This improves the detection of mutations in transient regime. It is shown that the decrease in the initial concentration of oligonucleotide probes by an order of magnitude causes only 1.5-2.5-fold decrease of fluorescence signals after hybridization of perfect duplexes for 3-12 h. At the same time, these conditions improve the discrimination between perfect and mismatched duplexes more than two-fold. A similar improvement may be obtained using an optimized dissociation procedure.     

The yeaS (leuE) gene of Escherichia coli encodes an exporter of leucine, and the Lrp protein regulates its expression

Overexpression of the yeaS gene encoding a protein belonging to the RhtB transporter family conferred upon cells resistance to glycyl-l-leucine, leucine analogues, several amino acids and their analogues. yeaS overexpression promoted leucine and, to a lesser extent, methionine and histidine accumulation by the respective producing strains. Our results indicate that yeaS encodes an exporter of leucine and some other structurally unrelated amino acids. The expression of yeaS (renamed leuE for "leucine export") was induced by leucine, l-alpha-amino-n-butyric acid and, to a lesser extent, by several other amino acids. The global regulator Lrp mediated this induction.     

Anthropometric multivariate structure and dermatoglyphic peculiarities in biochemically and morphologically different heterozygous groups

Multivariate analysis of the relationship between degree of heterozygosity at four blood group loci and the morphological variability in a human population was carried out. Additionally, the possibility that dermatoglyphic patterns correlate with biochemical and anthropometric variables was also investigated. A strong and significant increase in the frequency of morphologically multimodal individuals was observed, which paralleled the heterozygosity level. Discriminant analysis, by quantitative characters, of the closest pair of biochemically different samples yielded a satisfactory discrimination. Multiple correlations of each variable with all the others (18 traits), the communality of characters, the index of integration, and the Mahalanobis distances of the factor scores for each individual (all extracted from principal component analysis) were all indicative of the different multivariate structures of homo- and heterozygous individuals and thus supported the hypothesis that heterozygotes tend to cluster near the center of the joint multivariate distribution. The dermatoglyphic patterns showed a certain relationship with the morphological makeup of individuals. Correlations between biochemical heterozygosity at blood group loci and patterns of digital dermatoglyphics were rather irregular.     

Results of the comparative use of virological and bacteriological control of routine disinfection in maternity homes

Bacterial viruses were often detected in washings from different environmental objects; not infrequently, the inoculation of washings from the same objects resulted in the growth of Escherichia coli. The expediency of making parallel tests of washings from these objects for the presence of wild strains of bacterial and viral cultures both during the control of disinfection measures and the determination of the effectiveness of disinfection agents is shown.     

Effect of the heterogeneity of persons vaccinated, with respect to the state of their immune system, on the intensity of the immune response

Prior to the immunization of children aged 3-7 years with parotitis vaccine the state of their immune system was evaluated by the determination of the concentration of IgM, IgG and IgA, the ratio and absolute numbers of T- and B-lymphocytes, the intensity of the blast transformation of lymphocytes. This study revealed that the group of immunized children was essentially heterogeneous with respect to the state of their immune system: in 79.9% of the children all immunological characteristics were normal, in 20.1% of the children some deviations from the characteristics considered to be normal for their age (gammopathy, eosinophilia, the deficiency of T- and B-lymphocytes, a decrease in the intensity of their blast transformation, the leftward shift of the leukocytic formula) were noted. The intensity of humoral immune response in children with deviations from normal characteristics peculiar to their age was significantly lower than in children with normal immunological characteristics. On the basis of these results, the immunological rehabilitation of the risk group among the children to be immunized is recommended.     

The mechanism of the development of the epidemic process in Sonne dysentery

An epidemic outbreak of Sonne dysentery has been studied. The data of epidemiological monitoring before and after the epidemic have been analyzed. The real prognostication value of controlling the biological properties of Shigella sonnei and the increase of their intrapopulation heterogeneity at the period of the activation of the epidemic process of Sonne dysentery has been established.