Mobility of a One-Dimensional Confined File of Water Molecules as a Function of File Length

Saparov, Sapar M.; Pfeifer, Jochen R.; Al-Momani, Lo’ay; Portella, Guillem; Groot, Bert L. de; Koert, Ulrich; Pohl, Peter

doi:10.1103/physrevlett.96.148101

Cited by 51 publications

(70 citation statements)

References 38 publications

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“…The increase in D W compared with bulk water mobility may be a result of the reduced number of hydrogen bonds within the channel. Single-file water molecules with comparably high mobility also have been observed inside other membrane pores (19,25).…”

Section: Discussionmentioning

confidence: 80%

“…Previously, D W was calculated at ∼1.2 × 10 −3 cm 2 ·s −1 for singlefile water molecules inside wild-type KcsA (19). The number of open channels n was determined as the ratio G/g, where G and g denote the steady-state integral conductance of the whole lipid bilayer and the single-channel conductance of KcsA, respectively (8).…”

Section: Discussionmentioning

confidence: 99%

“…This allows the use of p f measurements for estimating D W (19). Conversely, the Stokes-Einstein relation D W = kT/6πηr may be used to estimate p f at room .…”

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confidence: 99%

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Filter gate closure inhibits ion but not water transport through potassium channels

Hoomann

Jahnke

Hörner

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The selectivity filter of K + channels is conserved throughout all kingdoms of life. Carbonyl groups of highly conserved amino acids point toward the lumen to act as surrogates for the water molecules of K + hydration. Ion conductivity is abrogated if some of these carbonyl groups flip out of the lumen, which happens (i) in the process of C-type inactivation or (ii) during filter collapse in the absence of K + . Here, we show that K + channels remain permeable to water, even after entering such an electrically silent conformation. We reconstituted fluorescently labeled and constitutively open mutants of the bacterial K + channel KcsA into lipid vesicles that were either C-type inactivating or noninactivating. Fluorescence correlation spectroscopy allowed us to count both the number of proteoliposomes and the number of protein-containing micelles after solubilization, providing the number of reconstituted channels per proteoliposome. Quantification of the per-channel increment in proteoliposome water permeability with the aid of stopped-flow experiments yielded a unitary water permeability p f of (6.9 ± 0.6) × 10 −13 cm 3 ·s −1 for both mutants. "Collapse" of the selectivity filter upon K + removal did not alter p f and was fully reversible, as demonstrated by current measurements through planar bilayers in a K + -containing medium to which K + -free proteoliposomes were fused. Water flow through KcsA is halved by 200 mM K + in the aqueous solution, which indicates an effective K + dissociation constant in that range for a singly occupied channel. This questions the widely accepted hypothesis that multiple K + ions in the selectivity filter act to mutually destabilize binding. membrane channels | protein reconstitution | knock-on mechanism | aquaporin | brain water homeostasis

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Filter gate closure inhibits ion but not water transport through potassium channels

Hoomann

Jahnke

Hörner

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…[25,26,27,28,29,30,31,32,33,34]). Such systems show the interesting feature of non-diffusive behavior of tracer particles, which stimulated experimental (see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

“…Such systems show the interesting feature of non-diffusive behavior of tracer particles, which stimulated experimental (see, e.g., Refs. [33,34]) and numerical [27,29,30,31] interest. Here we present a lattice model for ultrathin films in which multiple occupancy of a site is allowed (generalizing the single-occupancy model of Refs.…”

Section: Introductionmentioning

confidence: 99%

Spreading in narrow channels

et al. 2007

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We study a lattice model for the spreading of fluid films, which are a few molecular layers thick, in narrow channels with inert lateral walls. We focus on systems connected to two particle reservoirs at different chemical potentials, considering an attractive substrate potential at the bottom, confining side walls, and hard-core repulsive fluid-fluid interactions. Using kinetic Monte Carlo simulations we find a diffusive behavior. The corresponding diffusion coefficient depends on the density and is bounded from below by the free one-dimensional diffusion coefficient, valid for an inert bottom wall. These numerical results are rationalized within the corresponding continuum limit.

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Functional Studies of Synthetic Gramicidin Hybrid Ion Channels in CHO Cells

et al. 2007

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The function of a gramicidin hybrid ion channel in living Chinese hamster ovary (CHO) cells was investigated by the patch clamp method. The synthetic ion channel 1 consists of two cyclohexyl ether amino acids that link two mini-gramicidin strands. With 1 at a concentration of 1.0 microM, an increase in the whole-cell membrane conductance was observed after 1.37 min. The conductance showed larger currents when Cs(+) was used as charge carrier than when Na(+) and K(+) were used. In single-channel recordings with Cs(+) as charge carrier, the substance showed comparable single-channel amplitudes in the membrane of living cells and artificial black lipid bilayers. In addition to functioning as a cation channel, compound 1 appeared to be a water channel. Exposure of the CHO cells to an extracellular hypoosmotic solution did not substantially change the cell volume. Extracellular hypoosmotic conditions in the presence of 1 increased the cell size to 146.5 % that of the control. Thus, the synthetic hybrid channel 1 can function as a cation channel with some Cs(+) specificity, and as a water channel in CHO cells.

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Mobility of a One-Dimensional Confined File of Water Molecules as a Function of File Length

Cited by 51 publications

References 38 publications

Filter gate closure inhibits ion but not water transport through potassium channels

Filter gate closure inhibits ion but not water transport through potassium channels

Spreading in narrow channels

Functional Studies of Synthetic Gramicidin Hybrid Ion Channels in CHO Cells

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