1.D.96. The Stacked Imidazole I-Quartet Superstructure Channel (I-Quartet) Family
Water permeability through artificial water channels formed by stacked imidazole I-quartet superstructures increases when the channel water molecules are highly organized. Correlating water structure with molecular transport is essential for understanding the underlying mechanisms of (fast) water translocation and channel selectivity (Kocsis et al. 2018). Water molecules exhibit a dipolar oriented wire structure within chiral I-quartet water channels both in the solid state and embedded in supported lipid bilayer membranes (SLBs). X-ray single-crystal structures show that crystallographic water wires exhibit dipolar orientation. Quantitative measures of hydrogen bond strength, connectivity, and the stability of the dipolar alignment in a membrane environment uncovered the interplay between the dipolar aligned water structure and water transport through the self-assembled I-quartets (Kocsis et al. 2018). TC families 1.D.96, 1.D.142 and 2.B.46 are based on imidazole backbone structure.
Artificial channels can be constructed from amphiphilic compounds undergoing self-assembly that synergistically generate directional superstructures across bilayer membranes as noted above. These alignments may create a pore structure that controls the ionic conduction and translocate water and ions, sharing one pathway across a cell membrane. Licsandru et al. 2021 reported that the imidazole and 3-amino-triazole amphiphiles self-assemble via multiple H-bonding to form stable networks within lipid bilayers. The alignment of supramolecular assemblies influences the conduction of ions, envisioned to diffuse along a hydrophilic pathways. Several derivatives present subtle variations on the ion transport activities, dependient on the structures of hydrophilic head and hydrophobic components. Fluorinated compounds often outperform the corresponding non-fluorinated counterparts. Under the same conditions, the R enantiomers have higher activity than the S enantiomers (Licsandru et al. 2021).