Comment on “Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins”

Hörner, Andreas; Pohl, Peter

doi:10.1126/science.aap9173

Cited by 35 publications

(50 citation statements)

References 15 publications

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“…The even faster H 2 O transport dynamics reported for subnanometer CNTs, shown in Fig. 4A, were obtained at low pH where protonation of carboxylate groups at the nanotube rim likely plays a key role (14)(15)(16)(17).…”

Section: Qens Analysis Of Water Dynamics In Pti•h 2 Omentioning

confidence: 72%

“…However, although published illustrations often presume that H 2 O molecules travel single file in a "conga line" pattern through GO membrane assemblies, molecular dynamics simulations reveal evidence for the existence of bulk fluid regions trapped among the graphitic sheets that are involved in the flow process (10). Rapid water transport that more closely resembles the directional transport of single H 2 O molecules through AQP channels has been reported within subnanometerdiameter carbon nanotubes (CNTs) embedded in lipid membranes (14)(15)(16)(17). Here, we report diffusion of single H 2 O molecules on a time scale equal to that in AQP channels across the interlayer spacing and through the aligned C 12 N 12 H 3 ring pores within the stacked graphene-like layers of crystalline carbon nitride with a polytriazine imide (PTI) structure (18)(19)(20).…”

Section: Introductionmentioning

confidence: 99%

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Aquaporin-like water transport in nanoporous crystalline layered carbon nitride

et al. 2020

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Designing next-generation fuel cell and filtration devices requires the development of nanoporous materials that allow rapid and reversible uptake and directed transport of water molecules. Here, we combine neutron spectroscopy and first-principles calculations to demonstrate rapid transport of molecular H2O through nanometer-sized voids ordered within the layers of crystalline carbon nitride with a polytriazine imide structure. The transport mechanism involves a sequence of molecular orientation reversals directed by hydrogen-bonding interactions as the neutral molecules traverse the interlayer gap and pass through the intralayer voids that show similarities with the transport of water through transmembrane aquaporin channels in biological systems. The results suggest that nanoporous layered carbon nitrides can be useful for developing high-performance membranes.

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Section: Qens Analysis Of Water Dynamics In Pti•h 2 Omentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Aquaporin-like water transport in nanoporous crystalline layered carbon nitride

et al. 2020

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“…Molecular dynamics (MD) simulations indicate that the single-file water arrangement in the CNTP channel is the main reason for its very high water permeability ( 10 ). A survey of other fast water membrane transporters with similar water molecule arrangements in the channel indicates that another hallmark of this mode of transport is an activation energy, E a , value in the range of 4 to 6 kcal/mol, i.e., a value that is the same order of magnitude as the activation energy for the self-diffusion of water ( 6 , 24 , 25 ). To test whether this assumption also holds true for CNTPs, we measured their water permeability as a function of temperature ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Water-ion permselectivity of narrow-diameter carbon nanotubes

Aydin

et al. 2020

Sci. Adv.

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Carbon nanotube (CNT) pores, which mimic the structure of the aquaporin channels, support extremely high water transport rates that make them strong candidates for building artificial water channels and high-performance membranes. Here, we measure water and ion permeation through 0.8-nm-diameter CNT porins (CNTPs)—short CNT segments embedded in lipid membranes—under optimized experimental conditions. Measured activation energy of water transport through the CNTPs agrees with the barrier values typical for single-file water transport. Well-tempered metadynamics simulations of water transport in CNTPs also report similar activation energy values and provide molecular-scale details of the mechanism for water entry into these channels. CNTPs strongly reject chloride ions and show water-salt permselectivity values comparable to those of commercial desalination membranes.

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“…Such a disentanglement between the rate of a process and its activation energy is impossible because it violates fundamental thermodynamic laws. 99 Moreover, the measured DG ‡ t value exceeds the upper limit of water transport through a pore of $15 kcal mol À1 (see the preceding section). In their rebuttal in Science 116 as well as in their contribution in the current Faraday Discussions volume, 117 the authors do not provide evidence that water or ions pass the nanotubes.…”

Section: 100mentioning

confidence: 99%

Single-file transport of water through membrane channels

2018

Self Cite

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Water at interfaces governs many processes on the molecular scale from electrochemical and enzymatic reactions to protein folding. Here we focus on water transport through proteinaceous pores that are so narrow that the water molecules cannot overtake each other in the pore. After a short introduction into the single-file transport theory, we analyze experiments in which the unitary water permeability, p f , of water channel proteins (aquaporins, AQPs), potassium channels (KcsA), and antibiotics (gramicidin-A derivatives) has been obtained. A short outline of the underlying methods (scanning electrochemical microscopy, fluorescence correlation spectroscopy, measurements of vesicle light scattering) is also provided. We conclude that p f increases exponentially with a decreasing number N H of hydrogen bond donating or accepting residues in the channel wall. The variance in N H is responsible for a more than hundredfold change in p f . The dehydration penalty at the channel mouth has a smaller effect on p f . The intricate link between p f and the Gibbs activation energy barrier, DG ‡ t , for water flow suggests that conformational transitions of water channels act as a third determinant of p f .

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Comment on “Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins”

Cited by 35 publications

References 15 publications

Aquaporin-like water transport in nanoporous crystalline layered carbon nitride

Aquaporin-like water transport in nanoporous crystalline layered carbon nitride

Water-ion permselectivity of narrow-diameter carbon nanotubes

Single-file transport of water through membrane channels

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