Technical Comments

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

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Science  30 Mar 2018:
Vol. 359, Issue 6383, eaap9173
DOI: 10.1126/science.aap9173

Figures

  • Fig. 1 Comparison of the water pathways across membranes with embedded carbon nanotubes and reconstituted aquaporins.

    (A) Conceivably, water leaks at the interface between the nanotubes and lipid membrane. (B) Altering the position of the nanotubes in the membrane by neutralizing the charged carboxylate groups at their ends (red to black) alters leak size and thus membrane water permeability. (C) Aquaporins offer aqueous pores that efficiently channel water. Protein-lipid interactions prevent any water from passing along the outer channel wall.

Tables

  • Table 1 The unitary pore water permeability pf and the Gibbs activation energy barrier ΔGt are intricately linked (Eq. 3).

    Membrane porepf (cm3 s–1)
    (measured)
    ΔGt (kcal/mol)
    (measured)
    r (s–1)
    (calculated
    from ΔGt)
    pf,c (cm3 s–1)
    (calculated
    from ΔGt)
    pf,c/pf
    Aquaporin-15.3 × 10−13 (5)3.1 (12)5.3 × 10101.6 × 10−123.0
    Aquaporin-Z2.9 × 10−13 (5)4.0 (13)1.2 × 10103.5 × 10−131.2
    KcsA5.3 × 10−14 (5)5.1 (8)1.8 × 1095.4 × 10−141.0
    Gramicidin A1.6 × 10−14 (14)6.1 (15)3.3 × 1081 × 10−140.6
    Carbon nanotubes6.8 × 10−13 (1)24.1 (1)2.1 × 10−56.2 × 10−289.1 × 10−16

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