AFM, a tool for single-molecule experiments

Force versus elongation curves measured with AFM-related techniques reveal a detailed insight into material properties at the molecular level. Here an overview on different implementations of this technique is given. The lateral distribution of a receptor on a sample surface was determined by mapping the adhesion force with a corresponding ligand immobilized at the tip. A dextran pattern on a gold surface was measured by mapping the rupture length of the polymer. Stretching single dextran molecules revealed a structural transition in the polysaccharide backbone at forces of 750 pN. The unfolding of individual domains in the modular protein titin was observed and information about the rate dependence of the unfolding forces was obtained.