Dataset Information

Confined water-mediated high proton conduction in hydrophobic channel of a synthetic nanotube.

ABSTRACT: Water confined within one-dimensional (1D) hydrophobic nanochannels has attracted significant interest due to its unusual structure and dynamic properties. As a representative system, water-filled carbon nanotubes (CNTs) are generally studied, but direct observation of the crystal structure and proton transport is difficult for CNTs due to their poor crystallinity and high electron conduction. Here, we report the direct observation of a unique water-cluster structure and high proton conduction realized in a metal-organic nanotube, [Pt(dach)(bpy)Br]4(SO4)4·32H2O (dach: (1R, 2R)-(-)-1,2-diaminocyclohexane; bpy: 4,4'-bipyridine). In the crystalline state, a hydrogen-bonded ice nanotube composed of water tetramers and octamers is found within the hydrophobic nanochannel. Single-crystal impedance measurements along the channel direction reveal a high proton conduction of 10-2 Scm-1. Moreover, fast proton diffusion and continuous liquid-to-solid transition are confirmed using solid-state 1H-NMR measurements. Our study provides valuable insight into the structural and dynamical properties of confined water within 1D hydrophobic nanochannels.

SUBMITTER: Otake KI

PROVIDER: S-EPMC7029035 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Confined water-mediated high proton conduction in hydrophobic channel of a synthetic nanotube.

Otake Ken-Ichi KI Otsubo Kazuya K Komatsu Tokutaro T Dekura Shun S Taylor Jared M JM Ikeda Ryuichi R Sugimoto Kunihisa K Fujiwara Akihiko A Chou Chien-Pin CP Sakti Aditya Wibawa AW Nishimura Yoshifumi Y Nakai Hiromi H Kitagawa Hiroshi H

Nature communications 20200218 1

Water confined within one-dimensional (1D) hydrophobic nanochannels has attracted significant interest due to its unusual structure and dynamic properties. As a representative system, water-filled carbon nanotubes (CNTs) are generally studied, but direct observation of the crystal structure and proton transport is difficult for CNTs due to their poor crystallinity and high electron conduction. Here, we report the direct observation of a unique water-cluster structure and high proton conduction r ...[more]

PMID: 32071299

Similar Datasets

Project description:The acid-activated proton channel formed by the influenza M2 protein is important for the life cycle of the virus. A single histidine, His37, in the M2 transmembrane domain (M2TM) is responsible for pH activation and proton selectivity of the channel. Recent studies suggested three models for how His37 mediates proton transport: a shuttle mechanism involving His37 protonation and deprotonation, a H-bonded imidazole-imidazolium dimer model, and a transporter model involving large protein conformational changes in synchrony with proton conduction. Using magic-angle-spinning (MAS) solid-state NMR spectroscopy, we examined the proton exchange and backbone conformational dynamics of M2TM in a virus-envelope-mimetic membrane. At physiological temperature and pH, (15)N NMR spectra show fast exchange of the imidazole (15)N between protonated and unprotonated states. To quantify the proton exchange rates, we measured the (15)N T(2) relaxation times and simulated them for chemical-shift exchange and fluctuating N-H dipolar fields under (1)H decoupling and MAS. The exchange rate is 4.5 × 10(5) s(-1) for N?1 and 1.0 × 10(5) s(-1) for N?2, which are approximately synchronized with the recently reported imidazole reorientation. Binding of the antiviral drug amantadine suppressed both proton exchange and ring motion, thus interfering with the proton transfer mechanism. By measuring the relative concentrations of neutral and cationic His as a function of pH, we determined the four pK(a) values of the His37 tetrad in the viral membrane. Fitting the proton current curve using the charge-state populations from these pK(a)'s, we obtained the relative conductance of the five charge states, which showed that the +3 channel has the highest time-averaged unitary conductance. At physiologically relevant pH, 2D correlation spectra indicated that the neutral and cationic histidines do not have close contacts, ruling out the H-bonded dimer model. Moreover, a narrowly distributed nonideal helical structure coexists with a broadly distributed ideal helical conformation without interchange on the sub-10 ms time scale, thus excluding the transporter model in the viral membrane. These data support the shuttle mechanism of proton conduction, whose essential steps involve His-water proton exchange facilitated by imidazole ring reorientations.

Dataset Information

Confined water-mediated high proton conduction in hydrophobic channel of a synthetic nanotube.

Publications

Confined water-mediated high proton conduction in hydrophobic channel of a synthetic nanotube.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets