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Biomedical subjects

D S Chernavskii

Publications and source records attributed to D S Chernavskii.

15 recordsLinked to original sources
PubMed1989

Kinetic model of bacteriorhodopsin photocycle: pathway from M state to bR.

A model of the last parts of the bacteriorhodopsin (bR) photocycle is proposed on the basis of experimental data for the kinetic behavior of the 'O' intermediate during a temperature pulse in distilled water suspension. The model includes the previously proposed (but not well characterized) intermediate 'N' between the 'M' and 'O' states of bR. This intermediate exists in fast temperature-dependent quasi-stationary equilibrium with the red-shifted intermediate 'O' and has a maximum of absorption close to the bR spectrum.

Bacteriorhodopsins↗
PubMed1985

On the possibility of reduction of dissipative structure models to a simple form.

A multicomponent reaction-diffusion system containing two different space scales (contrasting system) is considered. It is shown that if the system answers several conditions enumerated, it can be reduced to a bicomponent system which describes a dissipative structure either of a peak or of a step type. While in the first case the original and the final systems are equivalent only in the neighbourhood of zero, in the second case the equivalence is more general as the solution of these systems does not leave the region for which the procedure of reduction was developed.

Biometry↗
PubMed1982

On the formation of unique dissipative structures.

We consider a simple model for the formation of dissipative structures. In general there exists a multitude of stable final states. We show, however, that when the diffusion constant increases during the development of the system, a stationary state is reached which does not depend on the choice of initial conditions. We also show that a uniquely defined final state builds up when the system is initially strongly excited on one side.

Diffusion↗
PubMed1981

On kinetics of phase transitions in cell membranes.

Phase transitions in a bicomponent lipid membrane are considered. It is shown that in this case metastable states practically do not arise and phase transitions are smooth and hysteresisless. An elastic frame on the surface of the membrane changes the character of phase transitions: they become sharp and hysteretic. The role of membrane phase transitions for regulation of cell processes is considered.

Cell Membrane↗
PubMed1980

Relation of the intensity of metabolism with the process of determination in embryonic cell. Comparison of the experimental data with theory.

Relation between the level of the power metabolism and the degree of the determination of the embryos was investigated by comparison of the experimental material with theory. It was shown that the high level of metabolism promotes the change of the system to a differentiated state (i.e. leads to the limitation of tissue potency). The lowering of metabolism intensity is connected with a dedifferentiation of the tissue (or with expansion of it potency).

Amphibians↗
PubMed1980

Electron tunneling process and the segment mobility of macromolecules.

New experimental data [Berg, A. I., Noks, P. P., Kononenko, A. A., Frolov, E. N., Khrymova, I. N., Rubin A. B., Likhtenstein, G. I., Goldanskii, V. I., Parak, F., Bukl, M. & Mössbauer, R. (1979) Mol. Biol. (USSR) 13, 81-89; Berg, A. I., Noks, P. P., Kononenko, A. A., Frolov, E. N., Uspenskaya, N. Y., Khrymova, I. N., Rubin, A. B., Likhtenstein, G. I. & Hideg, K. (1979) Mol. Biol (USSR) 13, 469-477] provide evidence that the electron tunneling process is connected to a special type of conformational transition (segmental transition) protein macromolecules in photosynthetic membranes. This problem is investigated with a simple mechanical model. It is shown that the segmental degree of freedom can play the role of the strongly interacting accepting mode for the electron tunneling process. The temperature dependences of the electron tunneling rate and the recoilless gamma-ray absorption of membrane-bound 57Fe, as an indicator of the intramolecular mobility, are calculated. The problem of energy storage in proteins is also discussed.

Biophysical Phenomena↗
PubMed1977

A mathematical model of periodic processes in membranes (with application to cell cycle regulation).

A mathematical model of the regulation of the cell cycle by the plasma membrane is suggested. The model is based on the hypothesis that structural transitions of the cell membrane play an important role in the regulation of cell division. Conditions of transition from the proliferating state to the resting state and back are investigated. Possible qualitative differences between models of the cell cycle of a normal and a tumour cell are pointed out.

Cell Cycle↗
PubMedDate not supplied

Cell surface and cell division.

A mathematical model of the regulation of cell division is suggested. The model is based on the hypothesis that the process giving rhythm to cell division is located in the cell membrane: i.e., the process of free-radical oxidation of membrane lipids. Much depends on the physical state of the membrane. In the membrane, phase transitions take place because of the changes in lipid composition. These transitions differ in normal and tumor cells: in normal cells they are sharp and hysteretic owing to the presence of a framework (membrane skeleton) on the surface of the membrane, while in tumor cells the integrity of the surface is violated so that the transitions are smooth. This model makes it possible to explain differences in the regulation of normal and cancer cell proliferation. Within the limits of the model, such phenomena as density dependent inhibition of growth, reverse transformation, influence of cyclic AMP and ions of Ca2+ on the cell cycle, the actions of serum and of proteases on the cycle, and so on, are explained. A rational scheme for the appearance of the selective damage found in tumor cells is proposed.

Animals↗
PubMedDate not supplied

Biological consequences of the physical organization of the plasma membranes of normal and tumor cells.

The differences in the physical organization of the membranes of normal and tumor cells are explained within the framework of the hypothesis of the presence of an intact framework on the surface of normal cells and the absence of it in tumor cells. An intact framework determines the possibility of existence of metastable states of the membrane and hysteresis phenomena in the lipid bilayer. The signals for transition to the S- and M-phases of the cycle are breakoffs of the metastable states, which occur only in the membranes of normal cells. The cell cycle in tumors is constructed only on physicochemical processes in the membrane without hysteresis phenomena, and the possibilities of regulating it are greatly weakened. This hypothesis permits: a) prediction of differences in the change in the microviscosity of the lipids of normal and tumor cells during their movement along the cycle and refinement of the concept of intactness of cells in the presence of a change in the microviscosity; b) elucidation of the role of the spreading of cells for the initiation of division in vitro; c) the proposal of a method of selective destruction of tumor cells with the aid of proteolytic and lipolytic enzymes; d) the proposal of an explanation for the weak antigenicity of many spontaneous tumors and the possibility of enhancing it. Experimental data on the properties of the membranes are discussed, and they are compared with the theoretical premises.

Animals↗