Complete aggregation pathway of amyloid β (1-40) and (1-42) resolved on an atomically clean interface

To visualize amyloid beta (A beta) aggregates requires an uncontaminated and artifact-free interface. This paper demonstrates the interface between graphene and pure water (verified to be atomically clean using tunneling microscopy) as an ideal platform for resolving size, shape, and morphology (measured by atomic force microscopy) of A beta-40 and A beta-42 peptide assemblies from 0.5 to 150 hours at a 5-hour time interval with single-particle resolution. After confirming faster aggregation of A beta-42 in comparison to A beta-40, a stable set of oligomers with a diameter distribution of similar to 7 to 9 nm was prevalently observed uniquely for A beta-42 even after fibril appearance. The interaction energies between a distinct class of amyloid aggregates (dodecamers) and graphene was then quantified using molecular dynamics simulations. Last, differences in A beta-40 and A beta-42 networks were resolved, wherein only A beta-42 fibrils were aligned through lateral interactions over micrometer-scale lengths, a property that could be exploited in the design of biofunctional materials.