Solid-State NMR Molecular Structural Analysis of Co-Assembled Peptide Nanofibers.

Co-assembling peptides rapidly form β-sheet or α-helical nanostructures when distinct but complementary amino acid sequences recognize one another. Since the same peptides resist self-assembly on their own, co-assembly can provide a means of controlling assembly processes. Precise control of molecular structure would enable specific nanoscale organizations of bio-active functional groups. Furthermore, it is possible to engineer co-assembling peptides for highly selective molecular recognition, making it possible to produce hydrogels via multiple parallel assembly processes. Using solid-state NMR methods originally developed for the structural analysis of amyloid fibrils, we have evaluated a series of designer co-assembling β-sheets and α-helices. Some systems adopt the user-intended molecular structures, but we also detected several unanticipated structural features, including lack of preference for specific molecular orientations and a post-assembly transformation from an α-helical to a β-sheet structure. Finally, we will discuss how solid-state NMR can guide new designs for peptide co-assemblies.