What are the preferred horizontal displacements of aromatic-aromatic interactions in proteins? Comparison with the calculated benzene-benzene potential energy surface

The data from protein structures from the Protein Data Bank and quantumchemical calculations indicate the importance of aromatic-aromatic interactions at large horizontal displacements (offsets). The protein stacking interactions of the phenylalanine residue show preference for large offsets (3.5-5.0), while the calculations show substantially strong interactions, of about -2.0 kcal mol(-1)