Noncovalent biological interactions studied by atomic force microscopy and other surface-sensitive methods

This dissertation contains studies on noncovalent biological interactions by atomic force microscopy (AFM). Various surface-sensitive techniques, including x-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (TOF-SIMS), and contact-angle measurements, were applied to characterize the modified surfaces. A unique Poisson statistical analysis method was applied to extract individual ligand-receptor unbinding forces and nonspecific interactions from the AFM force measurements.; The individual biotin-avidin and biotin-streptavidin unbinding forces were determined with the Poisson AFM method, and were comparable to the values reported by others using different methods. This validated the applicability of the Poisson method in the studies of biological interactions.; Loading-rate and temperature dependence of individual biotin-avidin bond-rupture forces were investigated. A hybrid thermodynamic-kinetic model was established to help interpret the temperature dependence of the bond-rupture forces and to extract important thermodynamic parameters. This work takes quantitative AFM studies to the next level by allowing energies to be determined from force measurements.