Peptide Self-Assembly From the Molecular to the Macroscopic Scale at Standard Conditions

We have prepared nanocomposites in one step by hydrolyzing wheat gluten (WG) with trypsin and then drying the solution. Some tryptic peptides from WG self-assembled into fibrous structures under benign conditions (37 °C, 6-8 pH) to form a reinforcing phase while the balance did not to form the matrix phase. Here we describe the characterization of the self-assembled fibers, which were hierarchically structured and showed organization from the nanometer to the micrometer scale. The basic building block of the fiber was a stack of β–sheets. Scanning and transmission electron micrographs showed large fibers about 10 - 15 µm in diameter and appeared to be bundles of 10 - 20 nm diameter fibrils. Fourier transform infrared spectroscopy, X-ray diffraction, and thioflavin-T binding assay indicated that the framework of the fibrils was composed of cross-β structures, where β-strands ran perpendicular to the fiber axis. Preliminary investigation suggested that the elastic modulus of the WG-based fibers was 0.16 ± 0.03 GPa, consistent with reported values for natural protein fibers. A scaling argument is offered for how modulus arises from interaction energy described by fiber helical pitch.