Ionolamellar liquid crystal of G-quadruplex in a protic ionic liquid

G-quadruplex structures, assembled from guanosine (G) or its derivatives, are significant for their close association with biological processes and their capacity to serve as good templates for constructing functional materials, but the research and applications of G-quadruplex structures are mainly confined to aqueous solutions (in water).

We report the experimental evidence of an ionolamellar liquid crystal of G-quadruplex assembled from underivatized guanosine, induced by metal ions (K⁺, Na⁺, Ca²⁺ and Sr²⁺) in a protic ionic liquid (ethylammonium nitrate). The stacking mode of G-quartets varies with borate ester content and the ratio of borate ester to guanosine (R_B/G) for K⁺, while remaining unchanged for Na⁺. For Ca²⁺ and Sr²⁺, the stacking mode is also changed by excess divalent metal ions, leading to chiral inversion with changing concentrations of guanosine, and exhibiting strong affinity for borate ester to stabilize G-quadruplex. Ionolamellar liquid crystal displays ionic conductivity, κ = 7.20 and 9.96 mS·cm^-1 for mono-and di-valent ions, respectively.

These results advance our understanding of the structures of G-quadruplex and the role of dynamic borate esters in ILs, and may offer a new option to design the ionolamellar liquid crystal and electrolytes for biomedical devices.