H-bond analysis was also performed for the mutant systems and the results for H-bonds with more than 40% consistency are shown in Table S3. Few of the alanine substitutions increase the number of interfacial H-bonds between nCOV-2019 RBD and ACE2. Interestingly, the ala-substitution at Y489A increased the number of H-bonds in the wild-type complex. Mutation in some of the residues having consistent H-bonds in the wild type complex such as Q498A and Q493A, stunningly maintain the number of H-bonds in the wild-type complex. This indicates that the plasticity in the network of H-bonds in RBM of nCOV-2019 can reshape the network and strengthen other H-bonds upon mutation in these locations. However, few mutations decrease the number of H-bonds from the wild-type complex. Alanine substitution at residue G502 has a significant effect on the network of H-bonds between nCOV-2019 and SARS-COV. This residue locates at the end of L4 loop near two other important residues Q498 and T500. This mutation breaks the H-bonds at these residues. Mutation K417A decreases the number of H-bonds to only 5 where the H-bond at residue Q498 is broken. This indicates the delicate nature of the H-bond from residue Q498 which can easily be broken upon ala-substitution at other residues. Furthermore, mutation N487 also decreases the number of H-bonds by breaking the H-bond at Q498.