Peptide models XXV. Side-chain conformational potential energy surface, E = E(chi(1),chi(2)) of N-formyl-L-aspartic acidamide and its conjugate base N-formyl-L-aspartatamide in their gamma(L) backbone conformations

Ab initio molecular computations were carried out on the gamma(L) backbone conformation of N-formyl-L-aspartic acidamide and its conjugate base N-form yl-L-aspartatamide at the HF/3-21G level of theory. All side-chain conforma tions were explored for the parent amino acid diamide and its conjugate bas e. Propionate ion, propionic acid, 3,3-difluoropropionate ion and 3,3-diflu oropropionic acid were used to model the side-chain in the anionic and neut ral compounds. (C) 2000 Elsevier Science B.V. All rights reserved.