Introduction Ligand molecules for a particular receptor can be attached to the tip of an AFM probe, transforming the probe into a sensitive, chemically selective biosensor for that recep- tor [Riener et al. 2003]. Molecular recognition force microscopy (MRFM) is a single-molecule AFM- based technique that relies heavily on nanoscale surface chemistry, nanoscale biochemical immobiliza- tion chemistry, and bioconjugation chemistry. In MRFM, single-mole- cule unbinding interactions between AFM probe-bound ligands and substrate-bound receptor pairs are observed and quantified one by one as the AFM cantilever approaches and then is subse- quently withdrawn from the sur- face many times. The nanoNewton- scale molecular unbinding events are generally detected by measur- ing the optical deflection of the flexible AFM cantilever. These force spectroscopy (FS) experi- ments can provide valuable infor- mation about the structure and dynamics of molecular unbinding events at the single-molecule level [Noy et al. 1997]. In addition to