Eukaryotic cells of living tissues are susceptible of physical deformations while maintaining their cellular integrity and function. The ability of the cell to resist deformation and to change shape is mainly ensured by the elasticity of branching actin cytoskeletal networks (with branching obtained via the Arp2/3 protein complex), the major constituents of the cell cytoskeleton. The cell membrane confines the cytoskeletal networks and controls its growth, its structural and its mechanical behaviour. In turn cytoskeletal filaments especially actin filament networks provide the cells with its mechanical stability and organization. Experimental research suggests that the stability of normal cells and their elastic shape changes to internally or externally generated force is closely related to the coupling between the cell-sized confinement effect and spatial and orientational ordering of branching actin cytoskeleton. However quantitative theoretical studies are still needed. We develop a grand canonical monomer ensemble model to study the structural properties of branching actin networks under cellular confinement and make quantitative prediction of the contribution of these confined networks to the mechanical properties and elastic stability of the cell within living tissues.
Other components that are essential to the cells mechanics and function are DNA and proteins. DNA is not just a passive molecular bearer of information but is an active molecule that is able to respond structurally and mechanically to cellular signals. These are in turn often mediated by specific responses to the biochemical and structural details of the binding protein. It is therefore important to investigate the structural and elastic properties of DNA and proteins. Coarse grained molecular dynamics and Monte Carlo models and tools have been developed to simulate the DNA study the structure and dynamical properties of DNA. We extend these tools to study the structural and mechanical properties of proteins and the protein-DNA interactions.