Fig. 2.

Atomic expansion dynamics of amyloid fibrils as a function of amino acid sequence and chain length. (A) Plots of the relative expansion of the amyloid fibrils formed by five peptides and proteins as a function of time (curves have been shifted for clarity). Upon initiation of the T-jump, there is a rapid (Fig. S2) expansion of between 3.2–4.2 $\times$ 10⁻⁴ by all of the amyloid fibril networks, irrespective of sequence or chain length, $n_{aa}$. (B) By determining the T-jump for each of the fibril networks (Fig. S1), the thermal expansion coefficients, α, can be plotted, along with experimental error bars. This physical quantity is inversely proportional to the square of the bond stiffness, k (right axis), and a simple GNM, together with values of α from the literature (19–21), can be used to explain the experimental results (see main text). A schematic of the fibril’s constituent β-sheets is shown (Inset) with individual β-strands, connected by interbackbone hydrogen bonds (black dashed lines), shown as cyan ribbons. The representative β-sheet image was created using Protein Data Bank (PDB) ID code 2M5N.