Dynamics of Membrane Adhesion:  The Role of Polyethylene Glycol Spacers, Ligand−Receptor Bond Strength, and Rupture Pathway<sup>†</sup>

2008-02-19T00:00:00Z (GMT) by Joyce Y. Wong Tonya L. Kuhl
Biological adhesion typically occurs through discrete cross bridges between complementary molecules on adjacent membranes. Here we report quantitative measurements of the binding distance between a lipid membrane functionalized with ligands on flexible polymer tether chains and a second membrane bearing complementary receptors using the surface force apparatus technique. The binding distance is shown to increase as a function of polymer tether length. Upon separation, adhesive failure occurs not at the strong ligand−receptor bond but primarily through the mechanical pullout of cross-bridging polymer tethers from the membrane. We summarize these measurements of complementary membrane adhesion dynamics using an energy-state diagram that encompasses the energetics of the polymer tether, ligand−receptor bond strength, and number of cross bridges formed.