We made use of the amber99sb-disp force field and a TIP4P-D water model . For the starting conformation we extracted four stacked subunits (chains A, C, E and G) from the published atomic structure PDB: 6r4r 22 , (Figure ), thereby choosing to simulate a single protofilament instead of the double protofilament. This allows us to drastically increase conformational sampling. Given the evidence that the single protofilament can exist on its own , as well as only having one mutational site at the filament-interface (V74A) which has a low Φ-value and is therefore not predicted to make any contacts in the transition state, this is a sufficient model for investigating the association of a monomer to the existing fibril end.