1.D.52 The Aromatic Oligoamide Macrocycle Nanopore (OmnNP) Family
Oligoamide macrocycles 1d and 1e, which carry membrane-compatible side chains and contain hydrophilic, noncollapsible cavities, mediate high ion fluxes across lipid bilayers, as demonstrated by results from 23Na NMR and planar bilayer conductance measurements. The measured transmembrane single channel currents are very high, rivaling those typically associated with pore-forming protein toxins. Thus, large, highly conducting channels based on nanopores formed by oligoamide macrocycles has been achieved (Helsel et al. 2008).
A series of rigid phenylene vinylene macrocycles and phenylene ethynylene macrocycles with various substituents have been investigated as transmembrane ion channels (Hu et al. 2016). The length and polarity of the substituents have a significant effects on ion channel formation and the mass transport efficiency.
Macrocycles with strong aggregation properties facilitate ion passage across lipid bilayers. Oligoamide macrocycles 29-H and 29-NH2 are effective Cl- channels with long-lasting single conductance states that are consistent with nm-sized pores. The PK+/PCl- is 9 for 29-H and 3.5 for 29-NH2. Thus, both channels are cation selective, but 29-NH2 shows enhancement for Cl- conductance (Gale et al. 2017). These two channels have the same outer surface but different internal functional groups.