Histones H1 and H5 interact preferentially with crossovers of double-helical DNA

The interaction of the linker histones H1 and H5 from chicken erythrocyte chromatin with pBR322 was studied as a function of the number of superhelical turns in circular plasmid molecules. Supercoiled plasmid DNA was relaxed with topoisomerase I so that a population with a narrow distribution of topoisomers, containing from zero to five superhelical turns, was obtained. None of the topoisomers contained alternative non-B-DNA structures. Histone-DNA complexes formed at either 25 or 100 mM NaCl final concentration and at histone-DNA molar ratios ranging from 10 to 150 were analyzed by agarose gel electrophoresis. The patterns of disappearance of individual topoisomer bands from the gel were interpreted as an indication of preference of the linker histones for crossovers of double-helical DNA. This preference was observed at both salt concentrations, being more pronounced under conditions of low ionic strength. Isolated H5 globular domain also caused selective disappearance of topoisomers from the gel, but it did so only at very high peptide-DNA molar ratios. The observed preference of the linker histones for crossovers of double-helical DNA is viewed as a part of the mechanism involved in the sealing of the two turns of DNA around the histone octamer.     

A genetic and physiologic study of mutations of T4 phage suppressing the lysis defect of gene stII mutants

A new gene rVI phage T4B is found. Mutations rVI belong to the class of r-mutations of T4B. Mutations rVI do not show the lysis inhibition after superinfection and determine the r-morphology of plaques on Escherichia coli CR63 lawn. Mutations rVI are gene-specific suppressors of stII lysis defect, but do not suppress the e lysis defect. Alleles rVI and rVI+ are co-dominated with regard to the ability to suppress the stII lysis defect. The suggest the stoichiometric character of rVI gene function. Mutations rVI increase the permeability of infected cells before the lysis. The gene rVI located between the genes 56 and 39 on the T4B genetic map, close to the gene 56. The still mutations described earlier (Krylov, Yankovsky, 1973) suppress the lysis defect of the am z25 mutant in the gene e. The suppression is manifested when infected bacteria develope only in the liquid media.     

Steam Condensation from a Moving Steam-Gas Mixture

To date, heat exchange has been studied to the greatest extent for the case of the condensation of pure still and moving steam as well as for the case of condensation from a still steam-gas mixture. There are hardly any papers available wherein a moving steam-gas mixture with a substantial content of noncondensable gases is considered. To investigate this process, an experimental workbench of the working section has been developed, which makes it possible to determine the local values of the heat transfer coefficient from the steam-gas mixture to the walls of cooled heat-exchange tubes at different parameters and velocities of the gas-steam mixture. In the first four rows of tubes of the working section, there is no cooling, and their function consists in a hydraulic stabilization of the flow. In the fifth and the sixth row of tubes, the wall temperature of the cooled heat-exchange tubes is measured for determining the heat transfer coefficients from the moving steam to the tube walls. The seventh row of tubes is also not under cooling. Measuring tubes with temperature sensors have been manufactured that make it possible to obtain the wall temperature for determining the heat transfer coefficient. The adopted scheme of steam motion and the measurement system make it possible to obtain correct results of the heat and mass transfer investigation in the course of steam condensation from a gas-steam mixture with a significant content of noncondensing gases. The studies on steam condensation from a moving steam-gas mixture have been carried out in the range of parameter ρw² = 9.5 ? 66 Pa and at a volume concentration of air in the steam amounting up to ν_air = 0.18. Convective heat transfer coefficient α values for the heat transfer from a moving steam-gas mixture to the wall of a cooling tube were obtained. At small values of parameter ρw² = 9.5 Pa and the volume fraction of the air content ν_air = 0.06 in the steam, the average heat transfer coefficient exhibits a decrease by a factor of two as compared with that inherent in the condensation of almost pure steam. At the values of parameter ρw² = 66 Pa and at ν_air = 0.06, the average heat transfer coefficient decreases by 1.3 times. The studies on almost pure steam are in good agreement with Berman’s dependence.     

Radiation-induced bistable centers with deep levels in silicon <Emphasis Type="Italic">n</Emphasis> <Superscript>+</Superscript>–<Emphasis Type="Italic">p</Emphasis> structures

The method of deep level transient spectroscopy is used to study electrically active defects in p-type silicon crystals irradiated with MeV electrons and α particles. A new radiation-induced defect with the properties of bistable centers is determined and studied. After keeping the irradiated samples at room temperature for a long time or after their short-time annealing at T ～ 370 K, this defect does not display any electrical activity in p-type silicon. However, as a result of the subsequent injection of minority charge carriers, this center transforms into the metastable configuration with deep levels located at E_V + 0.45 and E_V + 0.54 eV. The reverse transition to the main configuration occurs in the temperature range of 50–100°C and is characterized by the activation energy ～1.25 eV and a frequency factor of ～5 × 10¹⁵ s^–1. The determined defect is thermally stable at temperatures as high as T ～ 450 K. It is assumed that this defect can either be a complex of an intrinsic interstitial silicon atom with an interstitial carbon atom or a complex consisting of an intrinsic interstitial silicon atom with an interstitial boron atom.     

Asymmetry between sister cells in a cancer cell line revealed by chemical cytometry

We introduce instrumentation and methodology for two-channel chemical cytometry of sister cells-two cells born from division of the same mother cell. The method is based on capillary electrophoresis with laser-induced fluorescence detection and allows simultaneously probing multiple intracellular components in sister cells. To test the new technology, we compared the expression patterns of green fluorescent protein (GFP) between the sisters in cultured cancer cells stably transfected with a GFP-expressing construct. We found that all sister cells had detectable asymmetry in the GFP expression patterns with a confidence level of higher than 95%. To our best knowledge, this is the first reported observation of asymmetric patterns of protein expression in sister cells in a cancer cell line. The proposed technology can reliably detect minor differences in chemical contents between sister cells, which makes it a potentially indispensable tool in studying the molecular mechanisms of developmental processes. It will be especially valuable in quantitative studies of cells with complex proliferation kinetics (e.g., stem cells).     

A Nonlocal Image Denoising Algorithm Using the Structural Similarity Metric

Programming and Computer Software - A new image denoising algorithm is proposed. It is a version of the nonlocal means (NLM) algorithm and uses a metric based on the CMCS modification of the...