Binary Structure of Amyloid Beta Oligomers Revealed by Dual Recognition Mapping

Amyloid beta (A beta) oligomers are widely considered to be the causative agent of Alzheimer's disease (AD), a progressive neurodegenerative disorder. Determining the structure of oligomers is, therefore, important for understanding the disease and developing therapeutic agents; however, elucidating the structure has been proven difficult due to heterogeneity, noncrystallinity, and variability. Herein, we investigated homo-and hetero-oligomers of A beta 40 and A beta 42 using atomic force microscopy (AFM) and revealed characteristics of the molecular structure. By examining the surface of individual oligomers with sequential N- and C-terminus specific antibody-tethered tips, we simultaneously mapped the N- and C-terminus distributions and the elastic modulus. Interestingly, both the N- and C-termini of A beta peptides were recognized on the oligomer surface, and the termini detected pixel regions exhibited a lower elastic modulus than silent pixel regions. These two types of regions were randomly distributed on the oligomer surface.