arXiv subjects

Daria S. Roshal

Publications and source records attributed to Daria S. Roshal.

3 recordsLinked to original sources

arXiv2026

Nonequilibrium assembly of Lennard-Jones particles on a sphere

Studying physical mechanisms and common geometric principles underlying known spherical packings is crucial for rational design of synthetic nanocontainers. Here we model the growth of small spherical shells containing n<72 identical particles that have their own curvature and interact with each other via the Lennard-Jones potential. The shell assembly is assumed to be nonequilibrium and sequential: at each step, a new particle is attached to the most energetically favorable position, after which the system relaxes. Along with well-known structures of the smallest icosahedral viral protein shells, the proposed mechanism generates a wide range of shells exhibiting square-triangular surface order. Most of such shells are the models of synthetic or natural protein complexes that have octahedral or tetrahedral symmetries and perform various functions. We compare the obtained structures with those resulting from the equilibrium assembly and corresponding to global energy minima. Also, we consider the temperature-dependent stochastic assembly and use the double-minimum Lennard-Jones-Gauss potential to mimic anisotropic particle interactions.

cond-mat.soft↗

arXiv2024

Topological balance of cell distributions in plane monolayers

Most of normal proliferative epithelia of plants and metazoans are topologically invariant and characterized by similar cell distributions according to the number of cell neighbors (DCNs). Here we study peculiarities of these distributions and explain why the DCN obtained from the location of intercellular boundaries and that based on the Voronoi tessellation with nodes located on cell nuclei may differ from each other. As we demonstrate, special microdomains where four or more intercellular boundaries converge are topologically charged. Using this fact, we deduce a new equation describing the topological balance of the DCNs. The developed theory is applied for a series of microphotographs of non-tumoral epithelial cells of the human cervix (HCerEpiC) to improve the image processing near the edges of microphotographs and reveal the topological invariance of the examined monolayers. Special contact microdomains may be present in epithelia of various natures, however, considering the well-known vertex model of epithelium, we show that such contacts are absent in the usual solid-like state of the model and appear only in the liquid-like cancer state. Also, we discuss a possible biological role of special contacts in context of proliferative epithelium dynamics and tissue morphogenesis.

cond-mat.soft↗

arXiv2023

Topological properties and shape of proliferative and non-proliferative cell monolayers

During embryonic development, structures with complex geometry can emerge from planar epithelial monolayers and to study these shape transitions is of key importance for revealing the biophysical laws involved in the morphogenesis of biological systems. Here, using the example of normal proliferative monkey kidney (COS) cell monolayers, we investigate global and local topological characteristics of this model system in dependence on its shape. The obtained distributions of cells by their valence demonstrate a previously undetected difference between the spherical and planar monolayers. In addition, in both spherical and planar monolayers, the probability to observe a pair of neighboring cells with certain valences depends on the topological charge of the pair. The zero topological charge of the cell pair can increase the probability for the cells to be the nearest neighbors. We then test and confirm that analogous relationships take place in a more ordered spherical system with a larger fraction of 6-valent cells, namely in the non-proliferative epithelium (follicular system) of ascidian species oocytes. However, unlike spherical COS cell monolayers, ascidian monolayers are prone to non-random agglomeration of 6-valent cells and have linear topological defects called scars and pleats. The reasons for this difference in morphology are discussed. The morphological peculiarities found are compared with predictions of widely used vertex model of epithelium.

cond-mat.soft↗