Highly Conducting Transmembrane Pores Formed by Aromatic Oligoamide Macrocycles

Helsel, Amber Jade; Brown, Amy L.; Yamato, Kazuhiro; Feng, Wen; Yuan, Lihua; Clements, Aimee J.; Harding, Stephanie V.; Szabó, Gábor; Shao, Zongshu; Gong, Bing

doi:10.1021/ja807078y

Cited by 151 publications

(104 citation statements)

References 23 publications

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“…Note that, although other strategies (e.g., internal charge repulsion) 18 have been used with success, rigidity of the building blocks is a key factor in keeping synthetic nanopores from collapsing. [3][4][5][6][7][8][9] We hypothesized that the same solvophobic driving force in the folding of the linear oligocholates 17 would prompt 1 to stack in the z-direction (Scheme 1, right). In a largely nonpolar solvent mixture, the polar solvent molecules should phase-separate into the middle of the macrocycle and solvate the inward-facing polar groups.…”

Section: Resultsmentioning

confidence: 99%

Water-Templated Transmembrane Nanopores from Shape-Persistent Oligocholate Macrocycles

2010

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Hydrophobic interactions normally are not considered a major driving force for self-assembling in a hydrophobic environment. When macrocyclic oligocholates were placed within lipid membranes, however, the macrocycles pulled water molecules from the aqueous phase into their hydrophilic internal cavities. These water molecules had strong tendencies to aggregate in a hydrophobic environment and templated the macrocycles to self-assemble into transmembrane nanopores. This counterintuitive hydrophobic effect resulted in some highly unusual transport behavior. Cholesterol normally increases the hydrophobicity of lipid membranes and makes them less permeable to hydrophilic molecules. The permeability of glucose across the oligocholate-containing membranes, however, increased significantly upon the inclusion of cholesterol. Large hydrophilic molecules tend to have difficulty traversing a hydrophobic barrier. The cyclic cholate tetramer, however, was more effective at permeating maltotriose than glucose. Abstract: Hydrophobic interactions normally are not considered a major driving force for self-assembling in a hydrophobic environment. When macrocyclic oligocholates were placed within lipid membranes, however, the macrocycles pulled water molecules from the aqueous phase into their hydrophilic internal cavities. These water molecules had strong tendencies to aggregate in a hydrophobic environment and templated the macrocycles to self-assemble into transmembrane nanopores. This counterintuitive hydrophobic effect resulted in some highly unusual transport behavior. Cholesterol normally increases the hydrophobicity of lipid membranes and makes them less permeable to hydrophilic molecules. The permeability of glucose across the oligocholate-containing membranes, however, increased significantly upon the inclusion of cholesterol. Large hydrophilic molecules tend to have difficulty traversing a hydrophobic barrier. The cyclic cholate tetramer, however, was more effective at permeating maltotriose than glucose.

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Section: Resultsmentioning

confidence: 99%

Water-Templated Transmembrane Nanopores from Shape-Persistent Oligocholate Macrocycles

2010

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“…Details of preparing planar lipid bilayers is found else where 54,55 . Briefly, DPhPC (Avanti) lipid, dissolved at 10 mg ml − 1 in chloroform, was dried under a stream of nitrogen for a few minutes.…”

Section: Methodsmentioning

confidence: 99%

Self-assembling subnanometer pores with unusual mass-transport properties

et al. 2012

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A long-standing aim in molecular self-assembly is the development of synthetic nanopores capable of mimicking the mass-transport characteristics of biological channels and pores. Here we report a strategy for enforcing the nanotubular assembly of rigid macrocycles in both the solid state and solution based on the interplay of multiple hydrogen-bonding and aromatic π − π stacking interactions. The resultant nanotubes have modifiable surfaces and inner pores of a uniform diameter defined by the constituent macrocycles. The self-assembling hydrophobic nanopores can mediate not only highly selective transmembrane ion transport, unprecedented for a synthetic nanopore, but also highly efficient transmembrane water permeability. These results establish a solid foundation for developing synthetically accessible, robust nanostructured systems with broad applications such as reconstituted mimicry of defined functions solely achieved by biological nanostructures, molecular sensing, and the fabrication of porous materials required for water purification and molecular separations.

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“…27,28 Synthetic pore-forming agents in recent years have attracted many researchers' attention. Although a number of designs are available, the noncovalent forces utilized in the self-assembling are mostly limited to hydrogen bonds, 29−32 aromatic interactions, 33,34 and metal−ligand coordination. 35,36 The main evidence for the hydrophobically driven pore formation came from leakage assays and various control experiments.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Amphiphile Topology on the Aggregation of Oligocholates in Lipid Membranes: Macrocyclic versus Linear Amphiphiles

Widanapathirana

Zhao

2012

Langmuir

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A macrocyclic and a linear trimer of a facially amphiphilic cholate building block were labeled with a fluorescent dansyl group. The environmentally sensitive fluorophore enabled the aggregation of the two oligocholates in lipid membranes to be studied by fluorescence spectroscopy. Concentration-dependent emission wavelength and intensity revealed a higher concentration of water for the cyclic compound. Both compounds were shown by the red-edge excitation shift (REES) to be located near the membrane/water interface at low concentrations, but the cyclic trimer was better able to migrate into the hydrophobic core of the membrane than the linear trimer. Fluorescent quenching by a water-soluble (NaI) and a lipid-soluble (TEMPO) quencher indicated that the cyclic trimer penetrated into the hydrophobic region of the membrane more readily than the linear trimer, which preferred to stay close to the membrane surface. The fluorescent data corroborated with the previous leakage assays that suggested the stacking of the macrocyclic cholate trimer into transmembrane nanopores, driven by the strong associative interactions of water molecules inside the macrocycles in a nonpolar environment. Disciplines Chemistry CommentsReprinted (adapted) with permission from Langmuir 28 (2012) ABSTRACT: A macrocyclic and a linear trimer of a facially amphiphilic cholate building block were labeled with a fluorescent dansyl group. The environmentally sensitive fluorophore enabled the aggregation of the two oligocholates in lipid membranes to be studied by fluorescence spectroscopy. Concentration-dependent emission wavelength and intensity revealed a higher concentration of water for the cyclic compound. Both compounds were shown by the red-edge excitation shift (REES) to be located near the membrane/water interface at low concentrations, but the cyclic trimer was better able to migrate into the hydrophobic core of the membrane than the linear trimer. Fluorescent quenching by a water-soluble (NaI) and a lipid-soluble (TEMPO) quencher indicated that the cyclic trimer penetrated into the hydrophobic region of the membrane more readily than the linear trimer, which preferred to stay close to the membrane surface. The fluorescent data corroborated with the previous leakage assays that suggested the stacking of the macrocyclic cholate trimer into transmembrane nanopores, driven by the strong associative interactions of water molecules inside the macrocycles in a nonpolar environment.

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Highly Conducting Transmembrane Pores Formed by Aromatic Oligoamide Macrocycles

Cited by 151 publications

References 23 publications

Water-Templated Transmembrane Nanopores from Shape-Persistent Oligocholate Macrocycles

Water-Templated Transmembrane Nanopores from Shape-Persistent Oligocholate Macrocycles

Self-assembling subnanometer pores with unusual mass-transport properties

Effects of Amphiphile Topology on the Aggregation of Oligocholates in Lipid Membranes: Macrocyclic versus Linear Amphiphiles

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