Fig. 4.

Molecular models of DP (top) and YP (bottom) subgroups. Both models include the amino acids XPF (X = D or Y) and the amide group of L. The top is a type I reverse turn with a geometry that is consistent with the NMR data, including the close proximity of the D side-chain to the F amide proton and the F and L amide protons. The YP subgroup was drawn in one of many possible extended structures, representing a complete lack of close contacts seen in the DP peptides. The YP model and all amino acids not represented here from both groups are completely averaged. Models were made using Insight II (Biosym).