Aromatic amino acids, self-assembly morphology, fibrils


Excessive concentrations of the natural aromatic amino acids phenylalanine and tyrosine are characteristic of the severe genetic abnormalities known as phenylketonuria (PKU) and tyrosinemia, respectively. Within this context, this feature article authenticates claims that tryptophan can form amyloid-like supramolecular structures in vitro and is the first to propose potential mechanisms of tryptophan self-assembly, including hydrophobic and electrostatic interactions. Thioflavin T (ThT) fluorescence kinetics and transmission electron microscopy (TEM) data suggest the formation of amyloid-like fibrillar structures by natural aromatic amino acids in vitro. Additionally, the propensity of amino acid aggregation increases in the presence of sodium dodecyl sulfate (SDS). The structures formed by these amino acids are likely nucleated via hydrophobic interactions and elongated by π-π interactions. Fluorescence kinetics reveal a higher propensity of phenylalanine to self-assemble at pH 2, while tyrosine and tryptophan assemble best at pH 7, suggesting the necessity of zwitterionic charges in self-assembly.