We selected 150 representative structures of the TSE and used these as input to FoldX to calculate ∆∆G calc ‡-U . The agreement between ∆∆G exp ‡-U and ∆∆G calc ‡-U is very good with a linear correlation of 0.97 (Figure ) and shows that modeling ∆∆G calc ‡-U as the cost stemming from the removal of fibril state contacts is a reliable and self-consistent approximation for fibril elongation (Further analysis in the SI).