Introduction
AFM probes can be transformed into
sensitive, chemically selective biosensors
by attaching ligand molecules to the tips
of the probes. Single-molecule molecular
recognition force microscopy (MRFM) is an
AFM-based technique that relies heavily on
probes that have been modi? ed with ligand
molecules [Riener et al. 2003, Hinterdorfer
2004]. In MRFM, single-molecule
unbinding interactions between ligands
and complementary receptors that are
immobilized on a substrate are observed
and quanti? ed one by one as the AFM
cantilever approaches and subsequently
withdraws from the substrate. These force
spectroscopy (FS) experiments can provide
valuable information about the structure
and dynamics of molecular unbinding
events at the single-molecule level
[Noy et al. 1997]. The technique has
also been effectively applied to gain an
understanding of the intramolecular forces
involved in protein folding and polymer
elongation [Allison et al. 2002].