Figure 6.

(a) ¹³Cα secondary chemical shifts of Aβ₄₀(E22Q) (black) and Aβ₄₀(L17A/F19A/E22Q) (red) plotted as a function of residue. In principle, if the ¹³C^α secondary chemical shift of an amino acid residue is greater than 0.7 ppm, its conformation would be α-helical [35]; (b) Differences between Δδ¹³C^α (¹³C^α secondary chemical shift) and Δδ¹³C^β (¹³C^β secondary chemical shift) of Aβ₄₀(E22Q) (black) and Aβ₄₀(L17A/F19A/E22Q) (red) plotted as a function of residue. Δδ¹³C^α (or Δδ¹³C^β) was defined as the difference between the observed ¹³C^α (or ¹³C^β) chemical shift of an amino acid residue and its ¹³C^α (or ¹³C^β) chemical shift in a random coil conformation. If Δδ¹³C^α–Δδ¹³C^β for an amino acid residue is positive, its conformation would be α-helical. For a more detailed description of the relationship between the value of Δδ¹³C^α–Δδ¹³C^β and secondary structure of an amino acid residue please see the reference [34].