Fig. 2. HNP-1 binds to amyloid aggregates to induce its amyloid inhibition effects. (a) SPR sensorgrams of the concentration-dependent binding of HNP-1 to Aβ-, hIAPP-, and hCT-coated surfaces. Binding affinity between HNP-1 and amyloid peptides is determined by the binding constant (K_D) based on the Langmuir model (Fig. S5†). (b) Inhibition effect of HNP-1 on Aβ, hIAPP, and hCT seeds preformed at different aggregation stages by ThT fluorescence assay. Arrows indicate the time points of adding HNP-1 to specific amyloid seed solutions. (c) Binding of HNP-1 to the U-turn region of the Aβ pentamer determined from MD simulations via nonbonded interactions. At the Aβ/HNP-1 binding interface, Leu17, Phe19, Gly33, Leu34, Met35, and Val36 of Aβ showed a strong binding preference to Gln22, Cys4, Arg5, Ile6, and Pro7 of HNP-1 via hydrogen bonding and hydrophobic interactions. (d) Structural characterization and comparison of Aβ pentamers in the presence and absence of HNP-1 binding by using the RMSD (red) and β-content ratio (green). (e) Binding probability (%) of HNP-1 to Aβ residues.