Influence of local interactions on protein structure. III. Conformational energy studies of <i>N</i>‐acety‐<i>N</i>′‐methylamides of Gly‐X and X‐Gly dipeptides

Abstract

Abstract Conformational energy calculations using an empirical conformational energy program for peptides (ECEPP) were carried out on 20 N ‐acetyl‐ N ′‐methylamides of Gly‐X and X‐Gly depeptides, where X = Ala, Asn, Asp, Gly, Phe, Ser, Thr, Tyr, Val, and Pro, and also of Leu‐Gly. Each depeptde was found to have 25 or more low‐energy minima, except Gly‐Thr, which had only 11 low‐energy minima because of the stable side chian‐backbone hydrogen present in all low‐energy conformation. As a group, the stble chain‐backbone hydrogen bonds present in all low‐energy conformations. As a group, the Gly‐containing dipeptides were calculated in all low‐energy prpensity for formation of bends than the Ala‐containing depeptides. The X‐ Gly dipeptides were calculated to favor bends more than the Gly‐X dipeptides, primarlly because of the high stability of the type II bend in X‐Gly dipeptides. These results are in agreement with obseved occurrences of bends in the x‐ray structures of globular proteins. The calculated conformation properties were found to be in good agreement with experimental results.