Abstract
Transmembrane protein channels are of significant importance for the design of biomimetic artificial ion channels. Regarding the transport principles, they may be constructed from amphiphilic compounds undergoing self-assembly that synergistically generate directional superstructures across bilayer membranes. Particularly interesting, these alignments may impose an artificial pore structure that may control the ionic conduction and translocate water and ions sharing one pathway across the cell membrane. Herein, we report that the imidazole and 3-amino-triazole amphiphiles self-assemble via multiple H-bonding to form stable artificial networks within lipid bilayers. The alignment of supramolecular assemblies influences the conduction of ions, envisioned to diffuse along the hydrophilic pathways. Compounds 1-8 present subtle variations on the ion transport activities, depending the structure of hydrophilic head and hydrophobic components. Fluorinated compounds 3, 4 and 7, 8 outperform the corresponding non-fluorinated counterparts 1, 2 and 5, 6. Under the same conditions, the R enantiomers present a higher activity vs. the S enantiomers. The present systems associating supramolecular self-assembly with ion-transport behaviors may represent very promising unexplored alternatives for ion-transport along with their transient superstructures within bilayer membranes, paralleling to that of biology.
Highlights
Ion transport across the cell membrane is a highly important physiological process
The hydrophobic part is required in order to have a good affinity with the lipid bilayer membrane, while the hydrophilic part offers the possibility to interact with the ions or other hydrophilic metabolites, either in their hydrated or in their dehydrated forms (Hille, 2001)
Since the influence of this structural modification is tied to the lipid membrane, but was proven for antiport anion transporters, we aimed to reveal this influence of such a modification in the transport of cations; (c) a H-bonding urea/amide group as H-bonding directional selfassembling components; and (d) a heterocyclic hydrophilic head, namely imidazole and 3-aminotriazole for cation/proton binding and transport
Summary
Ion transport across the cell membrane is a highly important physiological process. Transmembrane protein channels, able to translocate cations across lipid bilayer with high permeability and selectivity (Lehninger et al, 2005). Inspired by the natural protein channels, synthetic artificial ion channels or carriers are fabricated as simplified models to study the driving factors for translocation and for their potential use as drugs, sensors or active membrane components. Synthetic ion channels are simple molecules, constructed by combining hydrophobic and hydrophilic groups. The hydrophobic part is required in order to have a good affinity with the lipid bilayer membrane, while the hydrophilic part offers the possibility to interact with the ions or other hydrophilic metabolites, either in their hydrated or in their dehydrated forms (Hille, 2001). There are two strategies to build synthetic ion channels: (a) the unimolecular channels are large molecules which are long enough to entirely cross the lipid bilayer membrane; they contain a lipophilic exterior and polar hydrophilic interior and (b) the self-assembled channels which are superstructures resulting from the self- assembly of a number of building blocks. The self-assembled channels having better solubility, allow a larger amount of active compound to act
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