Alexander M. Berezhkovskii

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Patterning of the terminal regions of the Drosophila embryo relies on the gradient of phosphorylated ERK/MAPK (dpERK), which is controlled by the localized activation of the Torso receptor tyrosine kinase [1-4]. This model is supported by a large amount of data, but the gradient itself has never been quantified. We present the first measurements of the(More)
Recent molecular dynamics simulations of water transport through the interior channel of a carbon nanotube in contact with an aqueous reservoir showed that conduction occurred in bursts with collective water motion. A continuous-time random-walk model is used to describe concerted transport through channels densely filled with molecules in a single-file(More)
The Bicoid gradient in the Drosophila embryo provided the first example of a morphogen gradient studied at the molecular level. The exponential shape of the Bicoid gradient had always been interpreted within the framework of the localized production, diffusion, and degradation model. We propose an alternative mechanism, which assumes no Bicoid degradation.(More)
A model of autocrine signaling in cultures of suspended cells is developed on the basis of the effective medium approximation. The fraction of autocrine ligands, the mean and distribution of distances traveled by paracrine ligands before binding, as well as the mean and distribution of the ligand lifetime are derived. Interferon signaling by dendritic(More)
Channel-forming proteins in a lipid bilayer of a biological membrane usually respond to variation of external voltage by changing their conformations. Periodic voltages with frequency comparable with the inverse relaxation time of the protein produce hysteresis in the occupancies of the protein conformations. If the channel conductance changes when the(More)
Single channels of Bacillus anthracis protective antigen, PA(63), were reconstituted into planar lipid membranes and their inhibition by cationic aminopropylthio-beta-cyclodextrin, AmPrbetaCD, was studied. The design of the highly efficient inhibitor, the sevenfold symmetrical cyclodextrin molecule chemically modified to add seven positive charges, was(More)
The steady-state flux through a singly occupied membrane channel is found for both discrete and continuum models of the solute dynamics in the channel. The former describes the dynamics as nearest-neighbor jumps between N sites, while the latter assumes that the molecule diffuses in a one-dimensional potential of mean force. For both models it is shown that(More)
The role of diffusion in the kinetics of reversible ligand binding to receptors on a cell surface or to a macromolecule with multiple binding sites is considered. A formalism is developed that is based on a Markovian master equation for the distribution function of the number of occupied receptors containing rate constants that depend on the ligand(More)
The problem of trapping of diffusing particles by nonoverlapping absorbing patches randomly or regularly located on a surface arises in numerous settings. Examples include diffusion current to ensembles of microelectrodes, ligand binding to cells, mass transfer to heterogeneous surfaces, ligand accumulation in cell culture assays, etc. see Refs. 1–15 and(More)
The paper deals with a diffusing particle that escapes from a cavity to the outer world through a narrow cylindrical tunnel. We derive expressions for the Laplace transforms of the particle survival probability, its lifetime probability density, and the mean lifetime. These results show how the quantities of interest depend on the geometric parameters (the(More)