Chirality-Assisted Ring-Like Aggregation of Aβ(1-40) at Liquid-Solid Interfaces: A Stereoselective Two-Step Assembly Process

Molecular chirality is introduced at liquid-solid interfaces. A ring-like aggregation of amyloid A beta(1-40) on N-isobutyryl-L-cysteine (L-NIBC)-modified gold substrate occurs at low A beta(1-40) concentration, while D-NIBC modification only results in rod-like aggregation. Utilizing atomic force microscope controlled tip-enhanced Raman scattering, we directly observe the secondary structure information for A beta(1-40) assembly in situ at the nanoscale. D- or L-NIBC on the surface can guide parallel or nonparallel alignment of beta-hairpins through a two-step process based on electrostatic-interaction-enhanced adsorption and subsequent stereoselective recognition. Possible electrostatic interaction sites (R5 and K16) and a chiral recognition site (H14) of A beta(1-40) are proposed, which may provide insight into the understanding of this effect.