The NAMD MD package was used to energy minimize and simulate the fibril models. The all-atom CHARMM36m force field was used to calculate potential energies and forces due to its improved treatment of secondary structure compared to CHARMM36. All simulations were performed under a constant temperature and pressure of 298 K and 1 atm, respectively. The Verlet velocity integration algorithm was used with a time step of 1 fs, and the SHAKE algorithm was employed to constrain heavy atom-hydrogen covalent bonds. Non-bonded interactions were calculated for atom pairs using a cutoff of 12 Å, and a switching function was used at distances greater than 10 Å to truncate the potential. The particle mesh Ewald method was used to calculate long range electrostatics. Visual and quantitative analysis of MD simulations was performed with Amber's cpptraj tool and VMD. The 24-mer fibril models were first energy minimized for 5000 steps with rigid backbone atoms using the conjugate gradient minimization scheme. Following this, we released the rigid backbone atoms and equilibrated the three fibril models for 2 ns with the aforementioned ψ-and C--O bond angle constraints for each polymorph taken from the Raman data. Following these constrained equilibration simulations, we released all the constraints and ran another 2 ns to observe the thermodynamic stability of the 24-mer fibrils. We collected ψand C--O bond angles, as well as inter-strand and inter-sheet distances from the constrained and unconstrained simulations.