Highly and Transparent Supramolecular Fibrils of Tyrosine

Various peptides and amino acids can self-assemble into fibers in a solution. These fibers can aggregate as amyloid in the organs of individuals with a certain genetic mutation and are therefore biocompatible. In this study we observed the mechanical properties of self-assembled fibrils of enantiomers of tyrosine, one of the essential aromatic amino acids found in living systems. We found the Young’s modulus of L-tyrosine fibers to be as high as 43 GPa with a point stiffness of 454 N/m. Young's modulus of D-tyrosine fibers was found to be approximately half that of L-tyrosine but significant nonetheless. These results demonstrate that tyrosine can form highly rigid bio-inspired structures. We also observed that films of L- tyrosine fibers have a transmittance of 65% while films of D-tyrosine fibrils and films from an equimolar mixture of both enantiomers were opaque. The study shows that chirality of the amino acids affects the molecular packing during supramolecular assembly resulting in structures with varying mechanical and optical properties.