The PDB2PQR server we used for protonating the proteins utilizes PROPKA 3.1 as a back end. While analyzing our results, we found that the server-selected protonation state was not the same across different receptor structures with a few of them having both Asp32 and Asp228 in the protonated state. Treating the protonation states more carefully by adding a step to check whether the protein was protonated as desired could have improved our predictions. Also, the existing pK a tools needs to be improved for more accurate prediction.