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 (0). Molecular dynamics simulations suggest that these intermediates are left-handed double helical beta-sheets. These findings have implications in the study of beta-sheet fibril formation, and in the molecular design of materials.