Conformational analysis of small peptides of the type Ac-X-NHMe, where X=Gly, Ala, Aib and Cage

The Ramachandran maps computed in vacuo using the different parameterizations of the Parm94 and Parm96 AMBER force fields, which are not explicitly parameterized for the Cage amino acid, compares favourably with the ab initio results performed at the HF level using the 6-31G* basis set. Analysis of these maps reveal the helical-conformational preferences of the Cage monopeptide, which has the potential to be incorporated in the design of constrained cyclic peptide analogues.