Molecular Dynamics Modeling of the SARS-CoV-2 Spike Protein at PH2 Through PH11.5

Abstract The spike glycoprotein (S protein) of the SARS-CoV-2 that has be studied extensively in vitro is modeled by all-atom molecular dynamics for its conformational states at six pH values ranging from 2 to 11.5. The MD simulations up to 3.7 T demonstrate interesting discoveries while confirming known facts. (1). At pH2, the protein’s time averaged RMSD is 62.5% higher than that of pH7, as the control group, and the receptor binding domain (RBD) deviates from that of pH7 by 200%. (2). For pH4 through pH10.5, the S protein remains relatively stable evident by the invariance of the side chain H bond counts and RMSD from pH7, suggesting high tolerance of the S protein to a wide range of pH values other than the extreme acidic and basic conditions. (3). For pH2 to pH4, the structure of the S protein alters significantly, suggesting the existence of a critical pH value at which the S protein responds to acid sharply. (4). In the residue-based relative entropy analysis, we identify several RBM and RBD residue clusters with maximum deviations that cause the overall protein structure changes.