Unexpectedly enhanced solubility of aromatic amino acids and peptides in an aqueous solution of divalent transition-metal cations

We experimentally observed considerable solubility of tryptophan (Trp) in a CuCl2 aqueous solution, which could reach 2-5 times the solubility of Trp in pure water. Theoretical studies show that the strong cation-π interaction between Cu2+ and the aromatic ring in Trp modifies the electronic distribution of the aromatic ring to enhance significantly the water affinity of Trp. Similar solubility enhancement has also been observed for other divalent transition-metal cations (e.g., Zn2+ and Ni2+), another aromatic amino acid (phenylalanine), and three aromatic peptides (Trp-Phe, Phe-Phe, and Trp-Ala-Phe). © 2016 American Physical Society.

Keywords

Amino acids, Solubility, Aqueous solutions, Metals, Transition elements, Cations, Tryptophan, Aromatics, Phenylalanine, Peptides

Citation

Shi, G., Dang, Y., Pan, T., Liu, X., Liu, H., Li, S., Zhang, L., Zhao, H., Li, S., Han, J., Tai, R., Zhu, Y., Li, J., Ji, Q., Mole, R. A., Yu, D., & Fang, H. (2016). Unexpectedly enhanced solubility of aromatic amino acids and peptides in an aqueous solution of divalent transition-metal cations. Physical Review Letters, 117(23), 238102. doi:10.1103/PhysRevLett.117.238102