Fig. 5.

The calculated backbone electrostatic energy difference (ΔE_dipeptide, see Materials and Methods) is plotted against the ab initio conformational energy difference (ΔE_{ab initio}) for various gas phase conformers of the alanine dipeptide, taken from ab initio studies in the literature. The geometry of each conformer, which is used in calculating E_dipeptide, is taken from the ab initio study. Similar results are obtained for two other ab initio studies of the alanine dipeptide (data not shown; see text). The data points for the C7_eq and C7_ax conformers are omitted because these conformers have an internal H-bond, whose energy is not well represented by using Coulomb's law. (A) In this study (25), data for six conformers could be shown here. The conformer coordinates were not published, and their geometries were built by using bond angles and distances from discover library. The slope of the line is 1.22 (R = 0.93). (B) In this study (24), data for four conformers could be shown here, and the published conformer coordinates could be used to give the conformer geometry. The slope of the line is 0.92 (R = 0.87).