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Vladimir P Zhdanov

Publications and source records attributed to Vladimir P Zhdanov.

12 recordsLinked to original sources
PubMed2006

Signaling between cells attached to a surface.

We present a kinetic model allowing one to classify likely scenarios of protein-mediated communication between attached cells of two distinct types. In our treatment, messenger proteins, synthesized in type-1 cells, are considered to penetrate the external membrane of these cells, diffuse in the extracellular medium, associate with the receptors in the external membrane of cells of both types, and induce intracellular signal transduction cascades, influencing the development of cells. Protein degradation inside and outside cells is taken into account as well.

Animals↗
PubMed2006

Self-sustained kinetic oscillations in CO oxidation over silica-supported Pt.

Isothermal self-sustained kinetic oscillations in CO oxidation over silica-supported Pt at near-atmospheric pressure were studied by combined in situ Fourier transform infrared spectroscopy and mass spectrometry. The use of a specially designed reactor and careful choice of the physical properties of the catalyst and reaction conditions made it possible to eliminate diffusion limitations, to determine the maximum CO oxidation rate per Pt site in the purely kinetic regime and to clarify the mechanism of the oscillations. Specifically, our results indicate that during the high reactive periods the reaction mainly occurs on the oxide surface.

Carbon Monoxide↗
PubMed2006

Adsorption and spontaneous rupture of vesicles composed of two types of lipids.

To analyze the adsorption of single vesicles composed of two types of lipids (e.g., zwitterionic and positively charged lipids or zwitterionic and negatively charged lipids), we propose a statistical model taking into account lipid-surface interactions, lipid-lipid lateral interactions, and vesicle bending energy. Our treatment specifies how these parameters govern vesicle adsorption, shows how the radius of the vesicle-surface contact area may depend on the vesicle composition, and clarifies the conditions for vesicle rupture.

Adsorption↗
PubMed2006

Grazers and grass: Monte Carlo simulations.

To illustrate the interplay between grazers and grass, we present a novel Monte Carlo model including grass-island growth, consumption of grass by grazers, and birth, migration and death of grazers. The rates of the former and three latter processes are assumed to depend on the environment so that the conventional mean-field approximation does not hold (in particular, the model takes into account that grass grows on the grass-island boundaries, and grazers are mobile and prefer to stay on the areas covered by grass). Due to the feedback between various processes, as expected, the model predicts stable regimes and irregular oscillations of the area of the grass islands and grazer population. The patterns observed are however different compared to those predicted by conventional Monte Carlo prey-predator models. Specifically, there is no tendency for grazers and grass to segregate. The mean-field version of the model is briefly discussed as well.

Algorithms↗
PubMed2005

Simulation of proliferation of neural stem cells on a surface with emphasis on spatial constraints on cell division.

We present Monte Carlo lattice simulations of proliferation of cells on a surface in the situation when the cell-cell adhesion is relatively strong and the cells may form islands and/or flattened hemispheres. The model parameters were chosen to mimic proliferation of adult rat neural stem cells (or, more specifically, adult hippocampal progenitor cells) deposited on polyornithine and laminin coated polystyrene. The results obtained show that the spatial constraints on cell division may result in slowdown of the exponential growth. Depending on the rules used for cell division, this effect may be either nearly negligible or appreciable. In the latter case, the scale of the deviations from the exponential growth is comparable with that observed in our experiments. In the simulations, the slowdown of the growth starts however somewhat earlier and occurs in a less abrupt manner. This seems to indicate that the spatial constraints on division of cells are not the main factor behind the experimentally observed termination of the growth.

Animals↗
PubMed2005

Monte Carlo simulation of bifurcation in the intracellular viral kinetics.

Intracellular viral kinetics are of special interest because the virion population inside an infected cell is well known to tend to grow exponentially and the corresponding kinetics may be unstable. To clarify the special features of such kinetics, we present Monte Carlo simulations taking into account the key steps of virion formation and competition of the host and viral mRNA for the host translation apparatus. Asymptotically, the model employed predicts either a stable steady state or 'ignition' with the unlimited viral growth. Under steady-state conditions, the mean square fluctuations of the viral genome and virion numbers are found to be appreciably larger than those expected on the basis of the Poissonian distribution. In the case of unstable kinetics, the simulations show the type of deviations from the corresponding mean-field results.

Algorithms↗
PubMed2004

A minimal generic model of bacteria-induced intracellular Ca2+ oscillations in epithelial cells.

The toxin alpha-hemolysin expressed by uropathogenic Escherichia coli bacteria was recently shown as the first pathophysiologically relevant protein to induce oscillations of the intracellular Ca(2+) concentration in target cells. Here, we propose a generic three-variable kinetic model describing the Ca(2+) oscillations induced in single rat renal epithelial cells by this toxin. Specifically, we take into account the interplay between 1), the cytosolic Ca(2+) concentration; 2), IP(3)-sensitive Ca(2+) channels located in the membrane separating the cytosol and endoplasmic reticulum; and 3), toxin-related activation of production of IP(3) by phospholipase C. With these ingredients, the predicted response of cells exposed to the toxin is in good agreement with the results of experiments.

Animals↗
PubMed2004

Stochastic kinetics of reproduction of virions inside a cell.

We analyze intracellular viral kinetics in the framework of the model incorporating viral genome replication, mRNA synthesis and degradation, protein synthesis and degradation, capsid assembly, and virion release from a cell. Due to the existence of the critical concentration of viral capsid proteins and other features of reproduction of virions inside a cell, the kinetics is demonstrated to exhibit three distinct initial stages. Specifically, (i) the exponential growth of the viral genome, mRNA and protein concentrations is followed by (ii) the transient stage to (iii) the steady-state regime. The formation of mature virions starts during the transient stage. Comparison of the kinetics, obtained by using the mass-action law and Monte Carlo (MC) technique, indicates that they are nearly identical during the initial exponential growth of the viral intermediates and also during the steady-state stage. The transition from the initial stage to the steady-state regime occurs however somewhat faster in the determenistic case even if the steady-state populations of virions and genomes are appreciable (e.g., about 250 and 500, respectively).

Capsid↗
PubMed2003

Perturbation of period-2 oscillations in catalytic reactions accompanied by surface restructuring.

We present Monte Carlo simulations illustrating the effect of periodic forcing on period-2 oscillations related to the interplay of catalytic reaction and surface restructuring. The oscillations are found to be fairly stable if the external frequency equals the main internal frequency. In contrast, perturbations with other frequencies may easily change the type of oscillation. In particular, perturbations with double frequency convert period-2 oscillations into period-1 oscillations with the imposed frequency.

Journal Article↗
PubMed2003

Water condensation kinetics on a hydrophobic surface.

Employing thermal desorption spectroscopy, we show that the effective probability of water condensation at low water vapor pressure on an octane film is much below unity at 100-120 K. This unusual finding is related to a small binding energy of H2O monomers on octane (approximately equal to 0.08 eV), requiring the formation of critical water clusters for condensation to occur. This results in strong temperature and impingement-rate dependencies of the water condensation rate and a nonlinear uptake as a function of dose time. All these features are rationalized quantitatively by a kinetic model of water condensation.

Journal Article↗
PubMed2002

Comment on "Monte Carlo simulations for a Lotka-type model with reactant diffusion and interactions".

Discussing the effect of adsorbate-adsorbate lateral interactions on the kinetics of heterogeneous catalytic reactions, Zvejnieks and Kuzovkov [Phys. Rev. E 63, 051104 (2001)] conclude that in the case of adsorbed particles the Metropolis Monte Carlo dynamics is meaningless and propose to use their own dynamics, which is equivalent to the Glauber dynamics. In this Comment, I show that these and other conclusions and prescriptions by Zvejnieks and Kuzovkov are not in line with the general principles of simulations of rate processes in adsorbed overlayers.

Comment↗