Rigid Tightly-Packed Amino Acid Crystals as Functional Supramolecular Materials.

The formation of ordered nanostructures by metabolites is gaining increased interest due to the simplicity of the building blocks and their natural occurrence. Specifically, aromatic amino acids possess the ability to form ordered supramolecular interactions due to their limited solubility in aqueous solution. Unexpectedly, L-Tyrosine (L-Tyr) is almost two orders of magnitude less soluble in water compared to L-Phenylalanine (L-Phe). However, the underlying mechanism is not fully understood as L-Tyr is more polar. Here, we explore the utilization of insoluble tyrosine assemblies for technological applications and their molecular basis by manipulating the basic building blocks of tightly-packed dimers. We show that the addition of an amyloid inhibition agent increases L-Tyr solubility due to the disruption of the dimer formation. The molecular organization grants the L-Tyr crystal higher thermal stability and mechanical property between three amino acids. Additionally, L-Tyr crystals are shown to generate high and stable piezoelectric power outputs under mechanical pressure in a sandwich device. By incorporating the rigid L-Tyr crystals into a soft polymer, a mechano-responsive bending composite was fabricated. Furthermore, the L-Tyr crystalline needles exhibit active photo waveguiding property, making them promising candidates for the generation of photonic biomaterial-based devices. The present work exemplifies a feasible strategy to explore physical properties of supramolecular self-assemblies comprised of minimalistic naturally-occurring building blocks and their applications in energy harvesting, photonic devices, stretchable electronics, and soft robotics.