Antibody recognition imaging by force microscopy

We have developed a method that combines dynamic force microscopy with the simultaneous molecular recognition of an antigen by an antibody, during ima ging. A magnetically oscillated atomic force microscopy tip carrying a teth ered antibody was scanned over a surface to which lysozyme was bound. By os cillating the probe at an amplitude of only a few nanometers, the antibody was kept in close proximity to the surface, allowing fast and efficient ant igen recognition and gentle interaction between tip and sample. Antigenic s ites were evident from reduction of the oscillation amplitude, as a result of antibody-antigen recognition during the lateral scan. Lysozyme molecules bound to the surface were recognized by the antibody on the scanning tip w ith a few nanometers lateral resolution. In principle, any ligand can be te thered to the tip; thus, this technique could potentially be used for nanom eter-scale epitope mapping of biomolecules and localizing receptor sites du ring biological processes.