Fragment Molecular Orbital Based Interaction Analyses on Complexes Between RBD Variants and ACE2

The spike protein plays an important role in the infection of SARS-CoV-2 to human cells, and the binding affinity of receptor binding domain (RBD) to angiotensin-converting enzyme 2 (ACE2) is of special interest. In this report, we present a series of interaction analyses for the RBD - ACE2 complex (PDB ID: 6M0J) and mutated complexes of UK (B.1.1.7 lineage), South Africa (B1.3.51) and Brazil (B1.1.248) types, based on the fragment molecular orbital (FMO) calculations. The effects of mutations are investigated in terms of inter-fragment interaction energies (IFIEs), indicating the higher affinities of RBD variants with ACE2.