FIGURE 3.

Schematic representation of the experiment, with the core of amyloid fibril depicted in gray, and blue lines representing intermolecular hydrogen bonds between the monomers. (a) The gold-covered AFM tip attaches covalently to C-103 on one of the monomers of the mica-adsorbed amyloid. (b) Retraction of the tip results in elastic stretching of the monomer between residue 103 and the beginning of the amyloid core region (black line). (c) When the pulling force exceeds a critical value, the monomer is extracted from the amyloid as an “all-or-none” event. This cartoon is for illustrative purposes only; it does not imply any specific structure of the PrP amyloid core, or any knowledge of pulling geometry in these experiments. The relative dimensions of the tip and protein molecules are not to scale.