AVS 46th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoM

Paper BI-MoM6
Specific Interactions between Bitoin and Avidin Studied by AFM using the Poisson Statistical Analysis Method

Monday, October 25, 1999, 10:00 am, Room 613/614

Session: Biosensor-Biology Interface
Presenter: T.P. Beebe, University of Utah
Authors: T.P. Beebe, University of Utah
Y.-S. Lo, University of Utah
N.D. Huefner, University of Utah
W.S. Chan, University of Utah
B.A. Shiley, University of Utah
F. Stevens, University of Utah
Correspondent: Click to Email
The interactions between biotin and avidin or streptavidin, a prototypical example of specific biological ligand-receptor systems, were studied by atomic force microscopy (AFM). A unique statistical analysis method which makes use of the properties of the Poisson distribution was applied, and the rupture strength of an individual interaction was obtained from the total pull-off forces measured by the AFM. Tip- and surface-modification chemistries were investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The Poisson analysis method has several advantages. It requires no assumptions about the surface energies or contact area between the AFM tip and the substrate, it is not limited by the force resolution of the instrument, and the number of measurements required to extract the individual unbinding force is significantly lower than that required by some other methods. It has been shown that bond rupture strengths are dependent on the rate and duration of force loading applied during the unbinding process. The dynamic nature of bond strengths under external forces has been explored in theory and by several computer simulations, however, only very few experimental studies have been reported. In the present study, we measure the unbinding force of the biotin-streptavidin pairs under various loading rates. The loading rate dependence of bond rupture forces and the comparison of our experimental data to the known thermodynamic properties of the system will be discussed.