Effect of Stereochemistry (Z and E) and Position of α,β-Dehydrophenylalanine (ΔPhe) on β-turn Stability

Abstract

Several model peptides containing α, β-dehydrophenylalanine (ΔPhe) in both Z and E configurations were studied for β-turn stability at the AM1 level of theory. Both configurations of ΔPhe are well able to stabilize β-turns in the backbone. However, the β-turns for peptides bearing Z-ΔPhe are energetically more stable than the E-counterparts. The difference in energies between the global minima of these peptides having the Z and E configuration of ΔPhe, is dictated by the size and stereochemistry of residues flanking ΔPhe. One distinct feature of E-ΔPhe is that it pushes peptides to adopt a Type II β-turn with the ΔPhe residue in the (i + 1) position of the turn. This unique feature may be exploited in peptide design.