Protein backbone atoms (C, Ca, O, and N) were not included to reduce the computational complexity. From these structures, hydrogen atoms were added using PyMOL v. 2.5.2 . Final geometries were obtained by freezing heavy atom coordinates and performing a DFT geometry optimization on all hydrogen atoms to preserve the close contact observed in the protein structure. These geometry optimizations were performed using the developer version 1.9-2018.11 of TeraChem with the global hybrid B3LYP DFT functional and the aug-cc-pVDZ basis set.