We show via 3D-heteronuclear NMR spectroscopy that Aβ_1–40 adopts a disordered conformational ensemble with fluctuating turns in DMSO_d6. Using NMR, we map the binding sites of three water-insoluble aggregation inhibitors to Aβ_1–40 in DMSO_d6 and discover remarkable differences in Aβ_1–40 recognition by a fourth inhibitor in H₂O versus DMSO_d6.