Kinetics of the reaction between muscle glycogen phosphorylase B and glycogen

Kinetics of glycogen binding by glycogen phosphorylase b has been studied by stopped flow and temperature jump methods. This reaction is followed by increase in light scattering whose amplitude depends upon the enzyme binding sites concentration of glycogen particles occupied by the enzyme. It has been shown that the complex formation has the first order with respect to enzyme and glycogen concentrations. Relaxation kinetics is compatible with proposed bimolecular reaction scheme. Microscopic rate constants of the forward and reverse reactions of glycogen binding by glycogen phosphorylase b are determined in temperature range from 12,7 to 30 degrees C. The possibility of diffusional control of the binding rate is discussed.     

Unfolding of tertiary structure ofHalobacterium halobium flagellins does not result in flagella destruction

The structure ofHalobacterium halobium R₁M₁ flagella is investigated by the methods of scanning microcalorimetry, circular dichroism, and electron microscopy. It is shown that melting curves of flagella in solutions with a different concentration of NaCl display only one peak of heat capacity that corresponds to one cooperatively melting domain. It is found that flagella do not dissociate after melting. The possible structural organization of archaebacterial flagella is discussed.     

The migration of radionuclides from global fallout in the trophic chains of biogeocenoses in arid zones

Radionuclide (137Cs and 90Sr) content in soil, plants, terrestrial vertebrates and invertebrates has been studied in Kalmyk ASSR, Turkmenian SSR, and Great Gobi Reserve (Mongolia). The content of radionuclides accumulated by wild animals in arid zone biogeocenoses and the patterns of radionuclide migration along food chains have been estimated. 90Sr was found to be involved in biological cycles with participation of soil and terrestrial organisms 3-23 times more intensively than 137Cs.     

Energetic aspects of CO oxidation in desulfovibrio desulfuricans

In cell suspension of Desulfovibrio desulfuricans B-1388, oxidation of CO as the only energy source is associated with reduction of SO42-. After a 2-h incubation of cells in 8% CO, 81% of the gas is converted. Oxidation of 1 mole CO results in formation of 0.23 mole H2S. Intracellular ATP content increases from 2.5 (control) to 8.3 nmoles/mg (during CO conversion). Dinitrophenol inhibits sulfate reduction and CO oxidation. CO dehydrogenase was detected in cytoplasmic and membrane cell fractions (59 and 34%, respectively).     

Population Genetic Analysis of the Association Between the <Emphasis Type="Italic">BRCA1</Emphasis> and <Emphasis Type="Italic">P53</Emphasis> Gene Polymorphisms and the Risk of Sporadic Breast Cancer

Polymorphism of two tumor-suppressor genes, BRCA1 and P53, was examined. DNA was extracted from blood leukocytes of the women affected with breast cancer (N = 151) and of the women with no clinical symptoms of tumor diseases (N = 191). Typing of the polymorphic variants was performed using PCR-RFLP method. It was demonstrated that the genetic structure of the patient group (taking into consideration BRCA1 and P53 polymorphic variants) differed from that of the control group. The group of genotypes, found exclusively among the patients, as well as the group of “ resistant” genotypes revealed predominantly among the controls, was described. Detection of the genotype A ₁ A ₁ B ₁ B ₁ S ₁ S ₁ C ₁ C ₁ F ₁ F ₁ J ₂ J ₂, whose frequency in control group was eight times higher than in the patient group, was an additional confirmation of the existence of “resistant” genotypes. These findings point to the association between the combinations of the BRCA1 and P53 allelic variants and the risk of breast cancer.__________Translated from Genetika, Vol. 41, No. 8, 2005, pp. 1115–1124.Original Russian Text Copyright © 2005 by Tarasov, Aslanyan, Tsyrendorzhiyeva, Garkavtseva, Lyubchenko, Altukhov, Mel’nik.     

Identification of a Mutant Gene Controlling Necrotic Cotyledons in Developing Seedlings of Arabidopsis thaliana

Genetic and molecular analyses of an Arabidopsis thalianamutant with necrotic cotyledons from the collection of insertion mutants obtained earlier were conducted. The mutation under study showed incomplete dominance and represented a single insertion of the T region of pLD3 vector used for transformation of germinating seeds to the plant genome during the creation of the collection. Using TAIL–PCR, a fragment of the mutant DNA adjacent to the left border of the T-DNA insertion was isolated and sequenced. Computer r-aided analysis showed that the insertion was located on the left arm of chromosome 1. The open reading frame containing the insertion has one exon and encodes a protein of 446 amino acids, whose function is unknown.     

Erythrocyte lysis in isotonic solution of ammonium chloride: theoretical modeling and experimental verification

A mathematical model of erythrocyte lysis in isotonic solution of ammonium chloride is presented in frames of a statistical approach. The model is used to evaluate several parameters of mature erythrocytes (volume, surface area, hemoglobin concentration, number of anionic exchangers on membrane, elasticity and critical tension of membrane) through their sphering and lysis measured by a scanning flow cytometer (SFC). SFC allows measuring the light-scattering pattern (indicatrix) of an individual cell over the angular range from 10° to 60°. Comparison of the experimentally measured and theoretically calculated light scattering patterns allows discrimination of spherical from non-spherical erythrocytes and evaluation of volume and hemoglobin concentration for individual spherical cells. Three different processes were applied for erythrocytes sphering: (1) colloid osmotic lysis in isotonic solution of ammonium chloride, (2) isovolumetric sphering in the presence of sodium dodecyl sulphate and albumin in neutrally buffered isotonic saline, and (3) osmotic fragility test in hypotonic media. For the hemolysis in ammonium chloride, the evolution of distributions of sphered erythrocytes on volume and hemoglobin content was monitored in real-time experiments. The analysis of experimental data was performed in the context of a statistical approach, taking into account that parameters of erythrocytes vary from cell to cell.     

Role of alkylhydroxybenzenes in bacterial adaptation to unfavorable growth conditions

The adaptogenic effect of the chemical analogues of alkylhydroxybenzenes (AHBs), bacterial extracellular autoregulators (the individual compound C7-AHB and its technical preparation Sidovit), was demonstrated for two pseudomonad species, Pseudomonas aeruginosa and P. fluorescens. The protective effect of AHBs resulted in increased growth rate and biomass accumulation in bacteria grown under suboptimal conditions within the species tolerance range. The adaptogenic effect of AHBs (10–50 μmg/l) was more pronounced under more unfavorable growth conditions. In the case of P. fluorescens, the individual compound C7-AHB increased the biomass yield by 30% under alkaline conditions (pH 9.5), when the growth rate decreased by 80–90% compared to the optimum (pH 5.5–7.5). The Sidovit preparation, containing a mixture of natural AHBs with C7-AHB as the main component, increased the growth rate of P. aeruginosa by 40–60% at nonoptimal temperatures (45 and 10°C) or under enhanced salinity (1% NaCl). The action of AHBs as regulators of the rpoS and SOS response stress regulons was demonstrated to be among the mechanisms of their adaptogenic effect, as was demonstrated with the relevant reporter genes in the model strains E. coli C600 thi, thr, leuΔ(pro-lac) with the osmE-lacZ and umuD-lacZ hybrid operons, respectively. AHBs are technologically and economically acceptable as adaptogenic supplements for bacterial preparations used in soil bioremediation and oil spillage removal under conditions unfavorable for microbial growth, including increased salinity, extreme pH, and fluctuating sub- or supraoptimal temperatures.