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The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues.

Horner A, Zocher F, Preiner J, Ollinger N, Siligan C, Akimov SA, Pohl P - Sci Adv (2015)

Bottom Line: We show that both the p f of those channels and the diffusion coefficient of the single-file waters within them are determined by the number N H of residues in the channel wall that may form a hydrogen bond with the single-file waters.The logarithmic dependence of water diffusivity on N H is in line with the multiplicity of binding options at higher N H densities.We obtained high-precision p f values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.

ABSTRACT

Channel geometry governs the unitary osmotic water channel permeability, p f, according to classical hydrodynamics. Yet, p f varies by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both the p f of those channels and the diffusion coefficient of the single-file waters within them are determined by the number N H of residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity on N H is in line with the multiplicity of binding options at higher N H densities. We obtained high-precision p f values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.

No MeSH data available.


Related in: MedlinePlus

DW depends on the number NH of hydrogen bonds that single-file water molecules may form with pore-lining residuesDW in nano-tubes assumes z = 2.6 Å and k0 = 0.1 p s−1 (13). pf for the bacterial potassium channel KcsA was calculated by applying Eq. 4 to our previously published stopped-flow curves (18). Equation 1 served to compute DW from the pf values of gramicidin, midigramicidin, minigramicidin (17), and KcsA.
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Figure 5: DW depends on the number NH of hydrogen bonds that single-file water molecules may form with pore-lining residuesDW in nano-tubes assumes z = 2.6 Å and k0 = 0.1 p s−1 (13). pf for the bacterial potassium channel KcsA was calculated by applying Eq. 4 to our previously published stopped-flow curves (18). Equation 1 served to compute DW from the pf values of gramicidin, midigramicidin, minigramicidin (17), and KcsA.

Mentions: Plotting NH against DW reveals a logarithmic dependence (Fig. 5). This observation is reminiscent of the logarithmic length dependence described for gramicidin derivatives (17). Because gramicidin conducts the single-file waters within the helix, we assume that all 30 backbone carbonyls may form hydrogen bonds. Midigramicidin and minigramicidin are four and eight residues shorter, respectively, which reduce NH. Their DW (Eq. 1) fits into the logarithmic dependence (Fig. 4). Finally, we recalculated pf for the bacterial potassium channel KcsA by applying Eq. 4 to our previously published stopped-flow curves (18). The corresponding DW (Eq. 1) is in line with the assumption that all 20 filter carbonyls are capable of contributing to NH (Fig. 4).


The mobility of single-file water molecules is governed by the number of H-bonds they may form with channel-lining residues.

Horner A, Zocher F, Preiner J, Ollinger N, Siligan C, Akimov SA, Pohl P - Sci Adv (2015)

DW depends on the number NH of hydrogen bonds that single-file water molecules may form with pore-lining residuesDW in nano-tubes assumes z = 2.6 Å and k0 = 0.1 p s−1 (13). pf for the bacterial potassium channel KcsA was calculated by applying Eq. 4 to our previously published stopped-flow curves (18). Equation 1 served to compute DW from the pf values of gramicidin, midigramicidin, minigramicidin (17), and KcsA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496530&req=5

Figure 5: DW depends on the number NH of hydrogen bonds that single-file water molecules may form with pore-lining residuesDW in nano-tubes assumes z = 2.6 Å and k0 = 0.1 p s−1 (13). pf for the bacterial potassium channel KcsA was calculated by applying Eq. 4 to our previously published stopped-flow curves (18). Equation 1 served to compute DW from the pf values of gramicidin, midigramicidin, minigramicidin (17), and KcsA.
Mentions: Plotting NH against DW reveals a logarithmic dependence (Fig. 5). This observation is reminiscent of the logarithmic length dependence described for gramicidin derivatives (17). Because gramicidin conducts the single-file waters within the helix, we assume that all 30 backbone carbonyls may form hydrogen bonds. Midigramicidin and minigramicidin are four and eight residues shorter, respectively, which reduce NH. Their DW (Eq. 1) fits into the logarithmic dependence (Fig. 4). Finally, we recalculated pf for the bacterial potassium channel KcsA by applying Eq. 4 to our previously published stopped-flow curves (18). The corresponding DW (Eq. 1) is in line with the assumption that all 20 filter carbonyls are capable of contributing to NH (Fig. 4).

Bottom Line: We show that both the p f of those channels and the diffusion coefficient of the single-file waters within them are determined by the number N H of residues in the channel wall that may form a hydrogen bond with the single-file waters.The logarithmic dependence of water diffusivity on N H is in line with the multiplicity of binding options at higher N H densities.We obtained high-precision p f values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Johannes Kepler University Linz, Institute of Biophysics, Gruberstr. 40, 4020 Linz, Austria.

ABSTRACT

Channel geometry governs the unitary osmotic water channel permeability, p f, according to classical hydrodynamics. Yet, p f varies by several orders of magnitude for membrane channels with a constriction zone that is one water molecule in width and four to eight molecules in length. We show that both the p f of those channels and the diffusion coefficient of the single-file waters within them are determined by the number N H of residues in the channel wall that may form a hydrogen bond with the single-file waters. The logarithmic dependence of water diffusivity on N H is in line with the multiplicity of binding options at higher N H densities. We obtained high-precision p f values by (i) having measured the abundance of the reconstituted aquaporins in the vesicular membrane via fluorescence correlation spectroscopy and via high-speed atomic force microscopy, and (ii) having acquired the vesicular water efflux from scattered light intensities via our new adaptation of the Rayleigh-Gans-Debye equation.

No MeSH data available.


Related in: MedlinePlus