Fig. 2. Activation barriers for the snapshots selected from the MM-MD simulation. These barriers corresponded to zero-point corrected total energies , calculated at the M06-2X/6-311++G(2d,2p):ff99SB level of theory. The purple and cyan points correspond to structures that react through the One Asp mechanism and the Two Asp mechanism, respectively. The lowest activation barrier (17.3 kcal mol^–1) was obtained, starting from the structure taken after 120 ns of MM-MD simulation. The dashed line provides a visual guidance for the chronological order of the barriers and does not correspond to an interpolation of the energies between them.