Due to the structural similarity between tyrosine and phenylalanine and the small size of those datasets, we augmented our data set by transforming tyrosine into phenylalanine and vice versa to generate additional close contacts. We removed the phenol group moiety from the set of tyrosine-galactose pairs to generate new phenylalanine interactions and carried out the reverse operation on the phenylalanine interactions, generating a 1.38 Å C-O bond para to the b carbon (Supporting Information Figure ). For all close contacts, hydrogens were added by PyMOL v. 2.5.2 and optimized using DFT (see Computational Methods). Two structures that formed residuecarbohydrate interatomic clashes (i.e., defined as having a distance relative to the sum of van der Waals radii of < 0.75 for any pair of atoms) after the addition of the tyrosine phenol group were removed from the dataset of newly generated tyrosine-galactose close contacts (Supporting Information Figure ). The resulting dataset contains 351 tryptophan, 197 tyrosine (i.e., 43 nonnative), and 199 phenylalanine (i.e., 154 non-native) close contacts.