Figure 4.
(A) One-dimensional free energy profile for the S-proteins of the SARS-CoV-2 (blue) and SARS-CoV (red) along the reaction coordinate RMSD. (B,C) Two-dimensional free energy profile for the S-proteins of the SARS-CoV-2 (B) and SARS-CoV (C) along the reaction coordinates RMSD and RBD bending angle. Colored lines are PaCS-MD trajectories for the successful down-to-up transition events. Green points represent the snapshots extracted from the last 60 ns of the six conventional MD simulation trajectories at the up-state plotted with a time interval of 5 ns. The dashed line represents the threshold value of the RBD angle (52.2°), above which the RBD domain will be open enough to access the receptor ACE2 as proposed in ref (25).