| dc.description.abstract | Cell crawling on
at substrates is a coordinated movement regulated by actin cytoskeleton,
myosin motors, cell membrane, and cell-substrate adhesion sites. Recent experimental advances
provided much information on cell crawling for theoretical modeling. However, most
of the theoretical models emphasized the roles played by the cytoskeleton, while experimental
probes reported force exerted on the substrate through the adhesion sites.
In this thesis, we use a simple one-dimensional active gel coupled to adhesion sites to
model the basic physics of cell crawling. In this model, we rst study the e ect of myosin
di usion on the distribution of slip bonds and catch bonds between cell and substrate.
After that, various migratory behaviors for cells with catch bonds are simulated by varying
contractility, binding energy, polymerization rate, and degree of cell polarization induced
by cytosol
ow asymmetry. The result points out that the motility of a cell is enhanced
when polymerization rate, contractility, or cell polarizability increases. One of the migratory
behavior is periodic migration. In previous theoretical studies, such behavior has only been
found when cell motility is coupled to the dynamics of actin polymerization activators that
is not included in our model. In our model, this state arises only for a cell with slow myosin
di usion, and it occurs between moving and rest states. Di erent from the slow myosin
di usion case, when the cell motility increases, a cell with fast-di using myosin motors
simply changes from rest to moving state. Finally, multipole expansion of traction force
shows that the force quadrupole vanishes in the rest state, and in the moving state has a
direction opposite to cell velocity. On the other hand, the force dipole is strongly correlated
to cell length. | en_US |