Bioen 326 2013 Lecture 24: Cell Adhesion. Motivation for Studying Adhesion Adhesive Structures Mechanics of bonds: slip, catch, ideal Mechanics of cell adhesion. Cells Bind to Biomacromolecules through Adhesive Molecules . Cells bind to biomacromolecules on cells and tissues
Motivation for Studying Adhesion
Mechanics of bonds: slip, catch, ideal
Mechanics of cell adhesion
from Kamm and Mofrad, Cytoskeletal Mechanics, 2006
drag force in flow pulls whole cell
motor proteins contract cell
We use constant approximation for x1t since bound and transition states have same spring constants
slip bonds: transition state is longer, so force exponentially increases unbinding rate, or decreases bond lifetime.
Hook model: transition state brings the hook together.
Allosteric model: allosteric change between long high-affinity to short low-affinity.
Like a door that must open inward – not safe in a fire, since force will keep it closed.
Cell adhesive molecules
Bacterial adhesive molecules
Intracellular bonds exposed to force
Yakovenko (2008) JBC
Marshall (2003) Nature
Yago (2008) J Clin Invest
Kong (2009) J Cell Bio
Akiyoshi (2010) Nature
If Bonds are Exposed to Force, Catch Bonds are the Rule
catch bonds also rupture at high force due to the slip pathway
yielding is viscoelastic, so depends on loading rate, but yielding force is in between, where catch bonds are strong.
catch bonds rupture at low force
Focal Adhesion complexes are evolved to have appropriate nanostructure for high strength. They are also evolved to localize signal transduction so cells can sense spatial information.