Sub-Persistence-Length Complex Scaling Behavior in Lysozyme Amyloid Fibrils

We combine atomic force microscopy single-molecule analysis with polymer physics concepts to study molecular conformations of lysozyme amyloid fibrils. We resolve a wavy structure of the fibrils in which the scaling behavior varies at multiple length scales. Bond and pair correlation functions, end-to-end distribution, and wormlike chain model identify three characteristic length scales. At short length scales (≈150 nm), there is a first bending transition of the fibrils corresponding to a bending length L(b). At larger length scales (>2L(b)), fibrils become pseudoperiodic and start to undulate. Finally, at length scales larger than the persistence length (~ μm), the fibrils become flexible and follow a 2D self-avoiding random walk. We interpret these results in terms of the twisting of the fibrils and the impact this has on the area moment of inertia and the propensity of the fibril to bend.