Here we extend this methodology to model the TSE of the addition of a monomer into PI3K-SH3 amyloid fibrils. We use the ten most robustly determined experimental Φvalues as constraints in molecular dynamics simulations. The experimental Φ-values are approximated as the fraction of fibril-like contacts (equivalent to native contacts in folding), where each residue's selection of fibril-like contacts is derived from the amyloid structure . The simulation is then biased to dissociate the protein from the end of the fibril and generate an ensemble of conformations that is consistent with the measured Φ-values 29 (Figure ). The resulting structural ensemble is effectively a partially bound ensemble, that should approximate the TS as the experimental constraints will arrest the dissociating protein within the free energy saddle-point for the fibril elongation reaction.