The NTD domain (residue 14 or 27-291) were truncated from the full-length S protein and both terminals are capped with ACE and NME, respectively. In order to get an intact structure, missing residues in flexible loops were modeled using SWISS-MODEL . The interfaces analysis was carried out using scripts of pymol2.5 with a cutoff of 0.75. Glycosylated NTD wild type and R246I mutation models were generated using Glycan Reader module available within CHARMM-GUI according to Table .