Biomimetic Approach for Highly Selective Artificial Water Channels Based on Tubular Pillar[5]arene Dimers

Abstract

Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water.H ere,w eq uantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes.T hey can transport % 10 7 water molecules/channel/ second, within one order of magnitude of the transport rates of AQPs,rejecting Na + and K + cations.The dimers have atubular structure,s uperposing pillar[5]arene pores of 5 diameter with twisted carboxy-phenyl pores of 2.8 diameter.T his biomimetic platform, with variable pore dimensions within the same structure,o ffers sizer estriction reminiscent of natural proteins.I ta llows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 pore.M olecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathwayst hrough the bilayer.O ver time, asignificant shift of the upper vs.lower layer occurs initiating new unexpected water permeation events through toroidal pores.

Artificial Water Channels: Towards Biomimetic Membranes for Desalination

“…We very recently discovered that modification of the rims of pillar[5]arene (5 Å diameter) may led to the narrowest constriction pores of 2.6–2.8 Å diameter within the same structure (Figure 14), [52] similar to the selective hourglass structure of AQPs [6] . This affords control of the translocation by size restriction along the resulting PAD channels at the selectivity filter level.…”

Multifunctional Pillar[n]arene-Based Smart Nanomaterials

“…Moreover, the rigid pillar backbone of PAs and its assembly in tubular structures have inspired its implementation in the development of artificial transmembrane channels for ion, water, and protein transport . Generally, PAs are functionalized with other macrocycles, peptide chains or other moieties, via click reactions or cabodiimide cross-linking to study the overall effect on the performance of the synthetic ion channels. − …”

“…The tubular assemblies were reminiscent of AQP (Figure b), with pore size variation from 5 Å up to 2.8 Å (Figure c), blocking cation transport, thus making them interesting for water desalination membranes. Increased length of the alkyl chains affected the channels water permeability, with the shortest one displaying the higher one, while the longest had a tendency to aggregate, decreasing the overall membrane permeability …”

“…Pillar[5]­arene (blue), with a diameter of 5 Å and the carboxyphenyl pore (red) being narrow and twisted of 2.8 Å diameter. Reprinted in part with permission from ref . Copyright 2020 John Wiley and Sons.…”

Pillar-Shaped Macrocyclic Hosts Pillar[n]arenes: From Simple Receptors to Supramolecular Assemblies

“…Discrete dimers can act as transportation channels for water molecules, but not for larger cations such as sodium or potassium cations (Figure 8b). 37 The normal pillar[5]arene cavity size is ca. 4.7 Å, but a discrete dimer has a narrow cavity on the benzoic acid group rim� The inter-molecular hydrogen bonds between the benzoic acid groups on the rim narrow the cavity size to ca.…”