FIGURE 2.

Force microscopy by AFM. (A) Force spectra on Au(111) epitaxially deposited on mica. Insets show the corresponding AFM images of the surface in the absence and presence of protein. On the surface without protein, the tip surface interaction is minimal or absent (black curve “approach”, pink curve “retract”). On the surface with protein, a retracting curve (pink) displaying three distinct phases of stretching of coiled-coil domains is observed. Adsorbed protein on the gold surface is indicated by a roughening of the surface as indicated in the AFM image. (B) Schematics of stretching myosin rod between the Au(111) surface and the tip. The cantilever tip picks up the protein at random positions on the protein along the length, not necessarily end to end.