Wendy Thomas, Ph.D.
Department of Bioengineering
E-mail: wendyt@uw...


TITLE:

"Bridging Length Scales from Nanoscale to Microscale Biomechanics"


ABSTRACT:

Many blood cells and pathogens bind to other cells or tissues in the presence of flowing fluid.
These diverse cells have evolved mechanisms to withstand and even utilize the associated drag
forces to strengthen adhesion, so that many of them display a shear enhanced adhesion in which
they detach at low shear but roll along the tissue surface or even stick firmly at higher
shear.  In this talk we use Escherichia coli as a model system to determine the role of various
molecules in this counterintuitive behavior. We use force spectroscopy to characterize the
mechanical properties of simple molecular complexes, including the adhesive molecules of E.
coli, which form catch bonds that are longer lived under increased tensile force, and the
tethers anchoring these bonds, which elongate long distances at a constant force.  We develop
mathematical models that describe these molecular behaviors quantitatively, and then
incorporate these models into simulations of whole cell adhesion, to explain how each property
contributes to the observed behaviors. Other pathogens and blood cells display convergent
evolution, because their adhesive bonds and tethers catch and elongate with similar mechanical
properties as those of E. coli, although they have no genetic or structural similarities. This
suggests that the principles established from studying this model system can be extended to a
large number of cells adhering in flow.