(a) Morphological differences between POPE and POPC headgroups. The nitrogen atom in the POPE headgroup is surrounded by three hydrogens, whereas in POPC the nitrogen is surrounded by three methyl groups. (b) A cross-section through the Aβ9–40 fibril, showing a two-peptide layer. Each peptide consists of an N-terminus β-strand (red), a turn region (green) and a C-terminus β-strand (blue). In the N-terminus and turn regions there are both positive (H13, K16, K28; blue) and negative (E11, E22, D23; red) residues. Polar sidechains are represented in green and the hydrophobic in grey, respectively.