Overview of Alzheimer’s Disease and Some Therapeutic Approaches Targeting Aβ by Using Several Synthetic and Herbal Compounds

Figure 5

(a) Sequence of Aβ₄₂ that is derived from human AβPP. (b) Structural constraints in Aβ₄₀ and Aβ₄₂ fibrils. NMR measurements of Aβ₄₀ fibrils have shown that residues 1–10 are unstructured and residues 11–40 adopt a β-turn-β fold. Side chain packing is observed between Phe19 and Ile32, Leu34 and Val36, Gln15 and Val36, and His13 and Val40 (orange dashed line). In Aβ₄₂ fibrils, residues 1–17 may be unstructured (in black), with residues 18–42 forming a β-turn-β fold. Molecular contacts have been reported within the monomer unit of Aβ₄₂ fibrils between Phe19 and Gly38 (blue dashed line) and between Met35 and Ala42 (black dashed line). In both Aβ₄₀ and Aβ₄₂, the turn conformation is stabilized by hydrophobic interactions (red residues) and by a salt bridge between Asp23 and Lys28 (purple dashed line).

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