How reliable could economic Hartree–Fock computations be in studying large, folded peptides? A comparative HF and DFT case study on N- and C-protected aspartic acid

In this study, potential energy hypersurfaces have been generated and analyzed for each of the nine possible backbone (BB) conformations for both the endo and exo forms of N-acetyl-l-aspartic acid N′-methylamide. Ab initio calculations were carried out at RHF/3-21G, RHF/6-31G(d), and B3LYP/6-31G(d) levels for all backbone conformations. The relative energies, as well as stabilization energies exerted by the sidechain (SC) on the backbone, were …