FIGURE 2.

A schematic diagram for derivation of the equation to correct the fibril width. The wide dotted line represents the directly observed image profile from AFM with a width of W. W^* is the actual width of the fibril. The actual fibril width can be derived as W^* = W − 2X, where H and R_c are the fibril height and the radius of curvature of the AFM probe tip, respectively. For EAK16-II fibrils and silicone crystal tips (R_c = 10 nm) used in the work, the actual width, W^*, is 15%–30% less than the observed width, W.