Left-Handed Helical Ribbon Intermediates in the Self-Assembly of a β-Sheet Peptide

We report the observation of intermediate structures in the self-assembly of the peptide KFE8 (FKFEFKFE), designed with alternating polar and nonpolar amino acids. Self-assembly was followed over time using atomic force microscopy (AFM), transmission electron microscopy (TEM), and circular dichroism (CD). Molecular dynamics simulations suggest that these intermediates are left-handed double helical β-sheets. These findings have implications in the study of β-sheet fibril formation, and in the molecular design of materials.