Vibrational circular dichroism of beta-hairpin peptides

Analysis of vibrational absorption and vibrational circular dichroism (VCD) for synthetic peptides designed to adopt beta-hairpin conformations reveal s characteristic well-resolved amide I absorption and VCD bands. All beta-h airpins with a type II' beta-turn segment yield an intense negative VCD ban d in the similar to 1643-1659 cm(-1) region, and a weak positive VCD band a t similar to 1693 cm(-1). These spectral features are diagnostic of beta-ha irpins cm and distinct from those observed for other secondary structures. Comparison of the electronic CD spectra of the beta-hairpin peptides Boc-Le u-Val-Val-DPro-Gly-Leu-Val-Val-OMe (1) and Boc-Leu-Phe-Val-(D)Pro-Gly-LeuPh e-Val-OMe (2) reveals that cross-strand aromatic interactions result in ano malous CD spectra in the region 200-240 nM for peptide 2. Similar anomalous electronic CD are observed in the three stranded beta-sheet peptide Boc-Le u-Phe-Val-(D)Pro-Gly-Leu-Val-Leu-Ala-(D)Pro-Gly-Phe-Val-Leu-OMe (3), while the VCD spectrum is characteristic of beta-hairpin conformations. The ident ical VCD spectra obtained for the peptides 1 and 2 emphasize the utility of VCD, as compared to electronic CD, in the conformational analysis of pepti des containing aromatic residues.