SnapShot: Force Spectroscopy and Single-Molecule Manipulation

The deflection of a cantilever is measured using a laser beam and position-sensing detector to obtain force and displacement for both imaging and force spectroscopy. In force spectroscopy, the cantilever is attached to one end of the protein or DNA sample while the other end is immobilized on the surface. The force and position of the tip are measured as the surface is moved away from the tip, providing the force-extension curve of the sample. High spatial resolution (0.5–1 nm); temporal resolution (>1 KHz); high force range (10–104 pN); high loading rate (10–105 pN/nm). Low force resolution compared to OT; difficult to operate under constant force; specificity can be difficult to control. High force and high loading rate pulling and interaction assays; protein unfolding dynamics; protein-ligand interactions; ligand-receptor interactions on live cells.