Polyhydrazide‐Based Organic Nanotubes as Efficient and Selective Artificial Iodide Channels

Abstract

Reported herein is a series of pore‐containing polymeric nanotubes based on a hydrogen‐bonded hydrazide backbone. Nanotubes of suitable lengths, possessing a hollow cavity of about a 6.5 Å diameter, mediate highly efficient transport of diverse types of anions, rather than cations, across lipid membranes. The reported polymer channel, having an average molecular weight of 18.2 kDa and 3.6 nm in helical height, exhibits the highest anion‐transport activities for iodide (EC50=0.042 μm or 0.028 mol % relative to lipid), whcih is transported 10 times more efficiently than chlorides (EC50=0.47 μm). Notably, even in cholesterol‐rich environment, iodide transport activity remains high with an EC50 of 0.37 μm. Molecular dynamics simulation studies confirm that the channel is highly selective for anions and that such anion selectivity arises from a positive electrostatic potential of the central lumen rendered by the interior‐pointing methyl groups.

Polypyridine‐Based Helical Amide Foldamer Channels: Rapid Transport of Water and Protons with High Ion Rejection

“…One-Pot Synthesis of Polymers P 30 to P 32 Very recently,w es howed that seven types of amide coupling agents (BOP,H ATU, HBTU,T BTU,T OTU, DEPBT,a nd DMTMM) can be applied to prepare fully hydrogen-bonded aromatic hydrazide polymers,o fahelical height of greater than 3nm, from their repeating monomer units. [11] Under identical reaction conditions,h owever, we found these amide coupling agents,together with many others such as PyBroP,T ATU, TCTU,TSTU,HCTU,and TFFH, do not yield even trace amounts of the fully hydrogen-bonded aromatic amide polymers P n ,l eaving starting materials (a) largely unreacted ( Figure 1c). These comparative observations are consistent with the hydrogen-bonded hydrazidelinked aromatic backbone being less rigid than the similarly hydrogen-bonded amide-linked aromatic backbone.…”

Polypyridine‐Based Helical Amide Foldamer Channels: Rapid Transport of Water and Protons with High Ion Rejection

“…Very recently, we showed that seven types of amide coupling agents (BOP, HATU, HBTU, TBTU, TOTU, DEPBT, and DMTMM) can be applied to prepare fully hydrogen‐bonded aromatic hydrazide polymers, of a helical height of greater than 3 nm, from their repeating monomer units . Under identical reaction conditions, however, we found these amide coupling agents, together with many others such as PyBroP, TATU, TCTU, TSTU, HCTU, and TFFH, do not yield even trace amounts of the fully hydrogen‐bonded aromatic amide polymers P n , leaving starting materials ( a ) largely unreacted (Figure c).…”

Anion Transmembrane Nanochannels from Pore‐Forming Helices Constructed by the Dynamic Covalent Reaction of Dihydrazide and Dialdehyde Units

“…For instance, anion channels constructed via macrocycles, [19–22] rigid rods, [23–24] peptides, [25] and organic cages [26] have been recently reported. Inspired by natural helical structures, shape‐persistent artificial ion channels designed via helical topology have attracted great interests owing to their unique structural features [27–30] . Aromatic helical (macro)molecules can generally self‐fold and even self‐assemble into highly ordered nanochannels.…”

“…Inspired by natural helical structures, shape-persistent artificial ion channels designed via helical topology have attracted great interests owing to their unique structural features. [27][28][29][30] Aromatic helical (macro) molecules can generally self-fold and even self-assemble into highly ordered nanochannels. Such synthetic helix channels possess uniform and intrinsic nanopores, and also provide a crucial structural basis for rational design of artificial channels.…”