Single Molecule Force Microscopy on Cells and Biological Membranes

Atomic force microscopy (AFM) enables high resolution topographic imaging of biological samples under near-physiological conditions. Therefore, the AFM is optimally suited for investigation of biological membranes and cell surfaces, as exemplified by studies on bacterial S-layers, purple membranes and cultured living cells. Topographic imaging allows visualizing single proteins and protein assemblies in native membranes, as well as substructures of live cells, such as cytoskeletal architecture. In addition to high-resolution imaging, the measurement of mechanical forces yields detailed insight into structure-function relationships of molecular processes in their native environment. In molecular recognition force microscopy, interaction forces between tip-bound ligands and membrane-embedded receptors can be studied under well-controlled buffer conditions and effector's concentrations. In case of low lateral density and inhomogeneous distribution of the target molecules in a cell membrane, fluorescence microscopy can help to guide the AFM tip to the membrane proteins of interest, which can subsequently be investigated by molecular recognition force microscopy.