SCF-MO STUDY OF THE POLYGLYCINE-II STRUCTURE

In order to get insight into the conditions that make polyglycine (PG) II a stable structure, the conformational features of three model mole cules closely related to the PGII conformation were investigated. The model molecules selected were glycine dipeptide (AGN), glycine tripept ide (AGGN), and glycine tetrapeptide (AGGGN). Environmental effects we re mimicked by means of formaldehyde molecules. The calculations were carried out at the SCF semiempirical level, using the AM1 method. The calculations show that of the three systems considered, only the AGGGN molecule presents a minimum energy conformation which corresponds to a PGII structure. The environmental conditions in which this conformat ion is found were also analyzed.