For the control scenario and scenarios B and C described in the previous section, initially the RBD and the ACE2 move closer to each other until they reach a mean distance of approximately 0.17 nm (1.7 Ångströms) and in that position they are maintained throughout the entire simulation trajectory, see Figure . To estimate the binding energy between the RBD and the ACE2, the potential LJ-SR energy was calculated using a GROMACS module. If this energy is lower, the union of the RBD with the ACE2 is stronger and more stable. Figure shows that the LJ-SR energy between the RBD and the ACE2 starts high (≈ -30 kJ/mol) and, as time progresses, it decreases until it reaches a mean value of approximately -250 kJ/mol. Also, at the beginning of the simulation, there is only one hydrogen bond between RBD and ACE2 and, as time progresses, the amount of hydrogen bonds rises to an average of 7 at 100 ns, see Figure . This leads to the conclusion that for the control scenario and scenarios B and C, the RBD binds to ACE2 with high affinity, and form a strong and very stable complex.