Surface Force Apparatus (SFA)
The SFA is a sensitive technique for measuring the range and magnitude of the molecular forces between two curved surfaces. This instrument quantifies intersurface separation with a resolution of 0.1nm, and the force measurement sensitivity is sufficient to quantify intermolecular interactions with energies as low as 0.6kcal/mole.
We use the SFA to measure the forces between cell surface proteins, in order to identify relationships between structure, molecular recognition, and biological adhesion. A major focus is on the intercellular adhesion proteins cadherins. In other recent investigations of molecular recognition in immunity, we used this approach to identify how the folded structures of multivalent receptors contribute to the recognition of pathogens such as HIV or contribute to susceptibility or resistance to viral infections.
A second NSF funded project is determining how the switchable surface properties of "smart" materials enable reversible protein (and cell) adsorption to biomaterials. We study water soluble polymers that are used in drug delivery, implants, and protein separations. Stimuli responsive polymers have been used to release intact cell sheets in tissue engineering. They are also used to trigger local drug release. The broad goal of these studies is to identify the molecular design rules that tune interactions between stimuli-responsive materials and proteins or cells. This work is in collaboration with Paul Braun (http://braungroup.beckman.illinois.edu/)