Boc-Val-Val-OMe (Aβ) and Boc-Ile-Ala-OMe (Aβ) crystallize in a parallel β-sheet arrangement but generate a different morphology

Both N - and C -protected dipeptides, Boc-Val-Val-OMe ( 1 ) and Boc-Ile-Ala-OMe ( 2 ), bearing sequence homogeneity with the C -terminus of Alzheimer's Aβ 39-40 and Aβ 41-42 , respectively, exhibit intermolecular hydrogen-bonded supramolecular parallel β-sheet structures in crystalline form. But the higher order aggregation of 2 showed a clear supramolecular cross-β-sheet structure unlike that of 1 . FESEM images indicated that, while 1 self-assembled into a highly organized two ended spear-like architecture, 2 formed a hollow hexagonal tube-like structure, in a methanol-water solvent mixture. These molecules self-assembled into the ordered structures which found to bind with the amyloid binding dyes thioflavin T (ThT) and Congo red. FT-IR and PXRD also support the formation of the β-sheet structure both in solution and in the solid state. These results may help in understanding amyloidogenesis and design principle of nanostructures. Crystal structures and morphologies of Boc-Val-Val-OMe (Aβ 39-40 ) and Boc-Ile-Ala-OMe (Aβ 41-42 ), the two consecutive dipeptides of the C -terminus of Aβ, are reported.