An ab initio exploratory study on selected conformational features of MeCO-l-Ala-l-Ala-l-Ala-NH-Me as a XxxYyyZzz tripeptide motif within a protein structure

A conformational study of the tripeptide model MeCO-l-Ala-l-Ala-l-Ala-NH-Me was carried out using ab initio molecular orbital computations in order to investigate the preferred conformations. At any particular instant, two alanine residues were fixed at the [βL] conformation and the third was varied for the nine possible minima present on the Ramachandran map. Subsequently, all minima were optimized. The conformational and energetic consequences of these findings are discussed in terms of relative stabilities and degree of backbone twisting or foldedness.