Concomitant occurrence of peptide 3(10)- and alpha-helices probed by NMR

Several initial experimental evidences have indicated that the terminally blocked -[L-(alphaMe)Val]8- sequence adopts a fully developed, right-handed 3(10)-helical conformation both in the crystal state and in structure-supporting solvents. More recently, the interesting property of this peptide to fold in solution both in the 3(10)- and in the alpha-helix has emerged. In this work, by using the NMR technique, for the first time we were able to monitor the coexistence of the 3(10)- and the alpha-helical structures at the residue level in the same peptide. The structural parameters characterizing these two strictly related, ordered conformations were precisely determined. We believe that this work provides a new insight into an important aspect of peptide 3D-structure with potential benefits for future investigations on peptide-based foldamers and the mechanism of protein folding.