Peptide Mixtures Can Self-Assemble into Large Amyloid Fibers of Varying Size and Morphology

Peptide mixtures spontaneously formed micrometer sized fibers and ribbons from aqueous solution. Hydrolyzed gliadin produced short, slightly eliptical fibers while hydrolyzed wheat gluten, a mixture of gliadin and glutenin formed round fibers of similar size. Mixing hydrolyzed gliadin with increasing molar amounts of myoglobin or amylase resulted in longer wider fibers that transitioned from round to rectangular cross section. Fiber size morphology, and modulus,were controlled by peptide mixture composition. Fourier transform infrared (FT IR) spectroscopy results showed that peptides experienced alpha to beta transitions forming an elementary cross-beta peptide condary structure, indicative of amyloids. Large fiber formation was observed to be dependent on hydrophobic packing between constituent peptides. A model was developed to show how the fiber morphology was influenced by the peptides in the mixture.