Scheme 1.

Structure of helical peptides and their assemblies. A) 3D structure of fiber-forming peptide Coil29 (PDB 3j89) and helical wheel projection of peptide sequence. From left to right: side view of nanofiber, top-down view of nanofiber, C-terminal interaction responsible for square formation. Lower cutout shows hydrophobic contacts that cause lengthwise elongation of nanofibers, and helical wheel shows peptide sequence. B) Design schematic for nanofibers incorporating kinking peptides and predicted changes caused by disruption of C-terminal interaction. C) Schematic of nanofibers terminated with capping peptides. Insets show predicted structure, with ends of fibers terminated with caps, leaving only hydrophilic residues on solvent-exposed helical faces. Helical wheel projections show mutations to hydrophobic residues in the Coil29 sequence.