The large number of combinations of the twenty natural amino acids that form proteins impart to them high structural flexibility and functional diversity. Quantum mechanical (QM), non-covalent interactions play a critical role in these diverse structures and functions. For example, non-covalent interactions between amino acids range from stronger charge-assisted or low-barrier hydrogen bonds and salt bridges to weaker hydrogen bonds and dispersive interactions. Computational, atomistic modeling provides essential insight into the dynamics and non-covalent interactions of proteins. Nevertheless, the size of proteins along with the timescales over which they dynamically rearrange means that classical molecular modeling is nearly exclusively used to understand protein structure-function relationships . This is at odds with the fact that proteins are known to carry out a number of inherently quantum mechanical functions, including shaping the electric field of the active site to influence chemical bond formation and altering the strength of noncovalent interactions critical for catalytic action.