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Biomedical subjects

A V Shishkov

Publications and source records attributed to A V Shishkov.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[Possibility to study cell membrane topography using tritium planigraphy].

The method of tritium planigraphy was adopted for the investigation of intact cells. Conditions for the incorporation of thermally activated tritium atoms in the erythrocytes are described. The accessibility of erythrocytes hemoglobin for tritium was compared to that of free hemoglobin. By comparing specific radioactivities of amino acids it was shown that the incorporation of the label into free hemoglobin was over 100 times higher than into that in erythrocytes. The cell membrane was highly tritiated. Thus the plasma membrane protects the cell inner regions from penetration of the hot tritium atoms. Tritium planigraphy can be used for studying the cell surface topography.

Amino Acids↗
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[Determination of the accessible surface of lysozyme and human serum albumin molecules by the total tritium labeling method].

Amino acids composing an accessible surface of lysozyme and human serum albumin (HSA) globules were determined by the total tritium labelling method. A good correlation between our data on the distribution of the tritium label for the lysozyme molecule and X-ray data on the tertiary structure for this macromolecule was received. Lysozyme was used as a standard for determining the accessible surface of the globule albumin. It was shown that the accessible surface of the albumin globule is substantially more hydrophobic (average accessible surface area of hydrophobic amino acids is 130 A2 in HSA and 20 A2 in lysozyme) than in lysozyme. The HSA molecule is characterized by high values of: the accessible surface area, the ratio of extended area to the folded one, and the surface roughness index. These data indicate that the HSA molecule is less compactly packed than lysozyme.

Amino Acid Sequence↗
PubMedDate not supplied

[Study of the three-dimensional structure of proteins by means of tritium labeling. II. Intramolecular distribution of tritium in the N-terminal part of myoglobin and the tertiary structure of protein].

The possible use of the method of 3H-label introduction by means of a 3H-atom beam for investigating the three-dimensional structure (surface) of proteins was studied. The intramolecular distribution of tritium in the N-terminal part of 3H-labelled sperm-whale myoglobin was studied. The results obtained are in good agreement with the X-ray analysis data on the polypeptide chain of the protein molecule. The possible use of this method for constructing precise three-dimensional models of polypeptides and proteins is discussed.

Animals↗
PubMedDate not supplied

[The mechanism of binding of sodium dodecyl sulfate by lysozyme].

It has been shown that the mechanism of complex formation changes at variation of the detergent concentration. At low concentrations the complex is stabilized, mainly, by hydrophobic interactions. The boded molecules are immobilized inside the globules. At concentrations close to critical micellization concentration only some of the molecules take part in such strong binding, while the rest form weak bonds and may be removed by gel filtrations. Presumably in this case electrostatic interactions dominate in binding processes. At concentrations exceeding critical micellization concentration complex formation is controlled by electrostatic association of protein with aggregates of the detergent's molecules, stabilized, like micelles by hydrophobic forces. The complex is unstable.

Kinetics↗
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[The structural characteristics of the polyribosomes in the rat liver studied by means of a tritium label].

Polyribosomes isolated from the rat liver in a medium with low ionic strength were irradiated by "hot" tritium atoms under conditions providing for the replacement of the hydrogen atoms located at the surface of polyribosomes by tritium. After fractionation of such polyribosomes, the radioactivity of the obtained fractions was measured and their proportions were calculated for the total surface accessible for the tritium atoms (in %), as well as their specific radioactivity. The material loosely associated with the polyribosomes and containing amino acyl-tRNA-synthetases is more radioactive than rRNA and r-proteins, especially concerning their specific radioactivity. This suggests that the material is organized as individual molecules located on the surface of ribosomes. The specific radioactivity of the RNA-component of this material (tRNA) is twice that of proteins, thus suggesting its surface localization in the composition of loosely associated material. Based on the pattern of labeling of rRNA and r-proteins of the native and preliminarily dissociated polyribosomes, we propose that the material, loosely associated with the polyribosomes, has affinity to both rRNA and r-proteins.

Animals↗
PubMedDate not supplied

[The concept of the "accessible surface" of the protein within the framework of tritium planigraphy. Experiment and calculation].

Tritium planigraphy allows one to determine the sterical accessibility of protein hydrocarbon fragments (CH, CH2, CH3 groups) for interaction with tritium atoms on condition of direct transit of the bombarding particles. Using lysozyme as a test system, it was shown to be possible to use these data for the description of protein accessible surface area in terms defined by Lee and Richards. The best agreement between experimental and theoretical results was achieved for an effective radius of the testing probe of 0.9 A. Coefficients were obtained that allowed calculation of the accessibility of amino acid residue as a whole using data about its hydrocarbon fragment accessibility.

Muramidase↗
PubMedDate not supplied

[Accessible surface and intramolecular mobility of proteins: study by method of tritium planigraphy].

The method of tritium planigraphy is used for determination of the accessible surface of a globular protein--lysozyme--and the accessibility of particular types of amino acid residues as a function of temperature in the range of 77-193 K. Protein powder with humidity 10 +/- 1% was used. As the temperature is changed from 77 to 160 K for all types of amino acid residues was obtained decreasing of inclusion of tritium label. All types of amino acid residues may be divided on the three groups: I. Accessibility rises under increasing temperature from 160 to 293 K (K, R, H, P, L); II. Accessibility not depends or slightly increases with the growth of temperature (C, V, A, I, Y, F); III. Accessibility strongly increases in the range of the temperature 260-293 K (S, T, G, D + N, E + Q). The reason of "cold denaturation" is perhaps the difference of behaviour of structural water molecules. Under increasing of temperature from 160 to 293 K change of accessibility was explained the growing of intramolecular flexibility of molecule. Under transition from 160 to 77 K for all types of residues is observed sensible change of spatial structure of the protein, which cannot be explained by only participation of dynamical characteristics.

Animals↗
PubMedDate not supplied

[Quantitative determination of the accessible surface of globular proteins by tritium planigraphy].

At the last time the term "accessible surface" is used for a description of protein structure. The tritium planigraphy was used for quantitative detection of the accessible surface. The experimental dependence of an interaction probability of the tritium atoms with globular proteins with calculated accessible surface areas was obtained. The method was proposed on the basis of the information about the reactivity of amino acids residues and was used for the determination of an accessible surface of parvalbumin III of pike.

Protein Conformation↗