FIGURE 4.

Number of steps at each z-coordinate (vertical axis is z axis; darker means more steps) plotted versus residue number (sequence shown), from 1–40 for Aβ40, a, and from 1–42 for Aβ42, b. Note that on residue 30, there appear three dark regions, corresponding to three peaks, whereas residues 26 and 28, for example, have four peaks. This result is important for our data analysis. Note also that the transbilayer conformation for Aβ42 is less common than for Aβ40 (compare the darkness, or number of steps, of the lowest peak on residue 40 for Aβ40 and Aβ42). The sequence of Aβ has polar residues shaded, hydrophobic residues underlined, and charged residues with charges indicated.