Fig. 3
From: The dipeptide conformations of all twenty amino acid types in the context of biosynthesis
Φ,ψ energy surfaces for dipeptides. Φ,ψ energy surfaces for dipeptides with residue types are shown in this order: A (Ala), C (Cys), D (Asp), E (Glu), F (Phe). Note that only the −72° ≤ Φ ≤ −60° region is relevant for Pro because of its cyclic structure involving the –N–CA–CB–CG–CD– atoms which restricts rotation around the Φ dihedral bond. A diagram showing the chemical structure for Pro is provided in order to illustrate this. Some members of this set of dipeptides appear to show defects (black colour) in certain regions. This has been anticipated and explained above (caption to Fig. 2)