Energy Parameters in Polypeptides. VI. Conformational Energy Analysis of the N‐Acetyl N′‐Methyl Amides of the Twenty Naturally Occurring Amino Acids

Abstract The conformational space accessible to the N‐acetyl N′‐methyl amides of the 20 naturally occurring amino acids has been explored extensively with the aid of empirical energy functions, and many minima have been located. The statistical weights for all minima with energy ≤ 3 kcal above the lowest for each residue have been calculated. In numerous cases, the conformation of lowest energy does not possess the highest statistical weight, thereby emphasizing the importance of considering the conformational librations when comparing theoretical and experimental results. The calculated minimum‐energy conformations, as well as those of highest statistical weight, are for the most part in good agreement with experimental results from studies of these compounds in solution and in the crystalline state.