Fig. 5.
Quantification of the water-accessible surface area of M2-TM from 1H spin diffusion buildup curves. (a) Normalized water-to-M2 spin diffusion buildup curves from the integrated intensities (64-16 ppm) of the 1D 13C DQ filtered spectra. Error bars are 1–2% on the normalized scale and are mostly smaller than the symbols. Best-fit buildup curves (lines) were obtained as described in the text. (b–d) Low-resolution structural models of the M2-TM proton channels used to obtain the best fits. (b) pH 4.5. (c) pH 7.5. (d) pH 7.5 with bound amantadine. Water: blue; protein: orange; lipid: brown; water-protein interface: green; amantadine: cyan. The bilayer thickness (44 Å) and pixel size (2 Å) of the 3D lattice are indicated.