The same Umbrella Sampling (US) protocol was used for all the 2D FESs presented in this work. The backbone dihedral angles phi and psi were used as the reaction coordinates (RC). Across each angle, 36 windows were used, spaced by 10 degrees, resulting in 1296 windows in total. The initial structures for each window were obtained at the MM level by first running 10 ps with a force constant of 10 kcal•mol -1 •rad -2 and then 100 ps with the force constant of 100 kcal•mol -1 •rad -2 . The latter force constant was used for all the subsequent US simulations, for both RCs. The sander input file with all the settings is provided in the supporting GitHub repository.