Improving the orientation-dependent statistical potential using a reference state

Statistical potentials are frequently engaged in the protein structural prediction and protein folding for conformational evaluation. Theoretically, to describe the many-body effect, pairwise interaction between two atom groups should be corrected by their relative geometric orientation. The potential functions developed by this means are called orientation-dependent statistical potentials and have exhibited substantially improved performance. However, none of the currently available orientation-dependent statistical potentials use any reference state, which has been proven to greatly enhance the power of distance-dependent statistical potentials in numerous previous studies. In this work, we designed a reasonable reference state for the orientation-dependent statistical potentials: using the average geometric relationship between atom pairs in known structures by neglecting their residue identities. The statistical potential developed using this reference state (called ORDER_AVE) prevails most available rival potentials in a series of tests on the decoy sets, although the information of side chain atoms (except the β-carbon) is absent in its construction.