Fig. 4.

Correlation between the backbone hydrogen bond formation and the side-chain electrostatic or hydrophobic interactions. Relative free energy, ΔG (in kcal/mol), as a function of the backbone CO… NH distance between Val-18 and Glu-22 (x axis) and the side-chain distance between Glu-22 and Lys-28 (y axis) in the simulation of Aβ(1–28) (A) and Aβ(10–42) (B) at pH 4. The distance between Glu-22 and Lys-28 is defined as the minimum separation between the carboxylate oxygen atom of Glu-22 and the amino nitrogen atom of Lys-28.