Search of the conformations of Val-dipeptide and Val-tripeptide by ab initio method and ABEEMσπ polarizable force field

ABEEM sigma pi polarizable force field (PFF) with fluctuating charges works well for searching stable conformations of Val-dipeptide and Val-tripeptide, showing importance of the polarization. The results demonstrate that ABEEM sigma pi PFF is able to search out all the 6 types of stable conformations of Valdipeptide and 34 types of stable conformations of Val-tripeptide that are just all exactly found by the calculations of ab initio B3LYP/6-311++G(d, p) and MP2/6-311++G(d, p) methods. In contrast, the force fields with the fixed-charges (FC), such as ABEEM sigma pi-FC, AMBER-FC 99sb and OPLS/AA-FC force fields can only search out less or much less numbers of stable conformations for them. (C) 2014 Elsevier B.V. All rights reserved.