On the other hand, Table shows those residues of ACE2 with better than -1 kcal mol -1 MMGBSA binding energy with RBD SARS-CoV-2 as compared with RBD SARS-CoV-1. It is clear from this table that the better interactions of these residues come from the electrostatic component of the Gibbs free energy, which can be attributed to higher number of hydrogen bonds established with RBD SARS-CoV-2 as compared with RBD SARS-CoV-1. Indeed, although the hydrogen bonds established with SARS-CoV-2 are not always established with the same residue, the percentage of the simulation time that a hydrogen bond is formed between ACE2 and RBD SARS-CoV-2 is 89.2%, 72.8% and 67.5% for ASP21, GLU18 and GLU20, respectively. All these three residues act as hydrogen acceptors, so that we add 3 hydrogen acceptor pharmacophoric points to our pharmacophore, adding an option in MOE that it is not needed that all these eight pharmacophoric points have to be fulfilled at the same time, but only 4. Table . Residues of ACE2 with differences in MMGBSA binding energies higher than -1.0 kcal mol -1 , with RBD SARS-CoV-2 and RBD SARS-CoV-1, showing also their van der Waals (VDW) and electrostatic components. All units in kcal mol -1 .