Potential energy curves, surfaces and hypersurfaces. A model to follow and understand the conformational transformations in amino acids

Abstract Applicability of two different concepts has been investigated for the exploration of conformational properties of flexible molecules, such as α- and β-amino acids. The first concept is based on multidimensional conformation analysis (MDCA), while the second one is calculation of potential energy curves, surfaces and hypersurfaces (PEC, PES, PEHS). In this study, we investigated four different molecules by ab initio molecular computations. The obtained PECs for histidine and methionine, and PEHS for β-alanine were evaluated and compared to PECs of smaller molecules (ethylimidazole and methyl–ethyl–thioether), with similar functional groups. Prediction of the minima, (i.e. MDCA) worked well for all molecules, however, it generally overestimates the number of minima in molecular systems different from alkanes. Histidine and methionine had several unpredicted minima due to spatial proximity of structurally distant atoms. In addition, MDCA was not able to predict the orientation of the minima of β-Ala. However, our results indicate that MDCA is a reliable tool in exploring molecular conformational properties.