Peptides and peptoids--a quantum chemical structure comparison.

Peptoids represent a very interesting structure alternative to peptides. Based on ab initio MO theory employing the 6-31G* and 3-21G basis sets and considering correlation energy, a systematic structure comparison between the basic structure units of peptoids and peptides is performed. The calculations show three minimum conformations denoted as C7 beta, alpha D, and alpha that do not correspond to conformers on the peptide potential energy hypersurface. The possibility of cis peptide bonds in the peptoids was examined. The solvent influence on the structure was estimated by means of various quantum chemical continuum models.