Browsing by Author "Azote, Somiealo"

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    Mechanical properties of cells and modelling of structural instabilities in tissues
    (Stellenbosch : Stellenbosch University, 2018-12) Azote, Somiealo; Müller-Nedebock, Kristian; Stellenbosch University. Faculty of Science. Dept. of Physics
    ENGLISH ABSTRACT : Cells have inherent mechanical properties that can be modelled physically. Statistical physics approaches permit the understanding of deformation dependence by modelling the various elements of the cytoskeleton and combining these with the constraints and physical properties of the cell membrane. When cells combine to form more complex structures, including, for example, epithelial structures, the resulting structure also needs to be understood. We wish to understand the mechanical contribution to the elastic properties and stability of the cell within the tissue when branching actin cytoskeletal network emerge or grow and their structure, spatial organisation and orientational ordering geometrically constrained by the cell membrane. Based on a grand canonical ensemble formalism by Frisch et al. [1] and Müller-Nedebock et al. [2], we model the structure of branching actin networks of living cell cytoskeletal filaments when these are rigidly contained with geometrical confining regions. The formalism allows a thermodynamic equilibrium calculation of density and orientational order density for fillaments and branch points. We find distinct local orientation, order parameter and density profiles for network filament segments, as the degree of branching and the ratio of persistence lengths of the filaments to the confining region size are varied. These results suggest the role of the confinement in the structural properties and organization of branching actin networks inside the confining region. We next investigated the contribution of the elastic properties of the networks to the elastic properties and stability of the cells within tissues by computing the free energies and forces of networks system. We find that tissue cells are stable against compression while cell under shear become unstable beyond a critical angle.