Before we begin our analysis, a few notes about nomenclature are in place. As can be seen in Table , we labeled all noncovalent interactions under consideration based on the participating residues in ACE2. For instance, the particular interaction involving residues D30 and H34 in ACE2, as well as residue V404 in SARS-CoV, will be denoted 1-SARS-n (n denotes a particular molecular structure representing the latter interaction; specifically, 1-SARS-a corresponds to the SARS-CoV-ACE2 crystal structure from Ref. ). Note that for the sake of good order, structure illustrations and names are also presented in Figure . Our calculated B3LYP/def2-TZVP noncovalent interaction energetics, as well as their deviation from ones calculated using the classical MMFF94 force-field, are presented in Table .