AVS 52nd International Symposium
    Biomaterial Interfaces Wednesday Sessions
       Session BI2-WeA

Paper BI2-WeA7
Interactions Between Membrane-Bound Receptors and Soluble Ligands Measured by AFM, QCM-D and SPR

Wednesday, November 2, 2005, 4:00 pm, Room 311a

Session: Cell-Surface Interactions
Presenter: Y. Lam, Duke University
Authors: Y. Lam, Duke University
S.M. Alam, Duke University
S. Zauscher, Duke University
Correspondent: Click to Email
Many proteins in the immune system are membrane bound, presented on the cell surface. Once bound to their soluble ligands, they facilitate interactions to initiate a foreign body response. To gain a deeper understanding of these interactions we initially investigated the bonds between soluble antigen and antibodies by single molecule force spectroscopy using an atomic force microscope (AFM). We immobilized monoclonal antibodies (mAb A32) specific to HIV-1 envelope glycoprotein gp120 on a substrate, and incubated this surface with gp120. This interaction between gp120 and mAb A32 causes a conformational change in gp120, exposing an epitope for a secondary mAb (17b) to bind. We measured the strength of interaction between gp120 and 17b by single molecule force spectroscopy using a cantilever tip decorated with 17b. AFM was also used to generate an energetic landscape of the binding pocket via pulling force experiments at different pulling rates. We also report on our measurements using membrane bound receptors, providing a more native environment for the system. Quartz crystal microbalance with dissipation (QCM-D) was employed to monitor the formation of protein-lipid bilayer constructs. Finally we report on measurements using surface plasmon resonance (SPR) to elucidate changes in affinity between membrane bound and immobilized soluble receptors. This detailed knowledge of receptor ligand interactions is essential to better engineer and tailor therapeutic treatments for various diseases.