As shown in Table , for ubiquitin with 76 residues full inclusion of all two-body interactions with the MFCC-MBE(2) method requires 11,104 single-point calculations. By applying a cutoff of 4 Å, this number can be reduced to 1,500, which is much more feasible considering that the single fragments and caps are as big as one amino acid and the dimer combinations have the size of about two amino acids. With these remaining dimer calculations, all main contributions to the total energy are still included, and the error of the conventional MFCC method is reduced by more than one order of magnitude.