Figure 7.

Geometrical characteristics of the AQP4 channel. (a) Tthe AQP4 channel radius averaged over 20 MD simulations (solid lines) for two different membrane bilayer thicknesses. Negative z values correspond to the cytoplasmic side of the membrane; the cytoplasmic channel entrance is located at z < −15 Å, the NPA residues are near z = 0 Å, and the selectivity filter is near z = +10 Å. The channel entrance structural parameters (entrance angle, depth, and pore radius) were measured from linear fitting (dashed lines) of the channel entrance radius. (b) Schematic plot illustrating the narrowing of the channel entrance in a thin bilayer (red dashed lines) compared to a thick bilayer (black lines) near the cytoplasmic entrance (bottom of drawing).