A designed beta-hairpin peptide.

A synthetic octapeptide, Boc-Leu-Val-Val-D-Pro-Gly-Leu-Val-Val-OMe (1) has been designed as a model for a beta-hairpin conformation. Circular dichroism spectra in various organic solvents reveal a single negative band at 214-217 nm consistent with beta-sheet structures. NMR studies in CDCl3 and C6D6 establish the solvent shielded nature of the Leu(1), Val(3), Leu(6) and Val (8) NH groups. Nuclear Overhauser effects are observed between Val(7) C alpha H and Val(2) C alpha H protons providing strong support for a beta-hairpin conformation. Several important diagnostic interresidue NOEs establish a Type II' beta-turn conformation for the D-Pro-Gly segment and extended conformations for the amino and carboxyl terminal tripeptide arms. The high solubility of the beta-hairpin peptide in organic solvents holds promise for the development of models for three and four stranded beta-sheets.