Hydrophobicity nonpolar face, amphipathic helices

In current structural. models of the Na+ channel, the four homologous a-helix domains pack together around a central pore formed by the four copies of the amphipathic helix 3. These helices probably are oriented so that most of their ionizable amino acid side chains face the aqueous space in the pore, whereas most of their nonpolar side chains face outward and interact with hydrophobic residues of other helices (fig. SI.7). The diameter of such a pore is... 

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