Interaction Energy Error Statistics of the 1UBQ Fragment Database.

Mean and variance of interaction energy deviations (kcal/mol) from reference energies (a mix of MP2/CBS and CCSD(T)/CBS) for the interacting fragment molecules present in ubiquitin. The set of fragments was divided into 42 van der Waals interactions and 50 polar interactions. The related plots are presented in Table S1. a) The calculated R-factor serves as an analogy to the residual minimized in crystallographic structure refinement. A desirable value of R-factor would be less than 0.1. b) The force field- based atomic charge parameters were scaled to yield correct net charge on each fragment system.