The mechanism of aggregation of Amyloid beta 1-40 (Aβ1-40) coated gold nano-particles ranging between 10 nm to 100 nm were investigated. The Aβ1-40 – coated nano-gold colloids aggregate at a particular pH value (pHo) due to the unfolded conformation of a peptide resulting in peptide networking. The formation of the aggregation can be identified by the red-shift of gold SPR (Surface Plasmon Resonance) band. Therefore, a spectroscopic investigation as a function of the concentration of Aβ1-40 allowed us to monitor gold aggregation process quantitatively for the first time. The aggregation mechanism was considered to be a nano-size dependent. For example, the 20 nm gold colloid particle exhibited sharp rise of aggregation formation at γ20 nm= [number of Aβ1-40]/[number of gold colloid] ~ 400 with λ(1) ~ 0.5 nm/pmol, where λ(1) Is the first derivative of SPR peak wavelength as a function of concentration of Aβ1-40. On the other hand, the 50 nm gold colloid particle exhibited very moderate rise with λ(1) ~ 0.01 at γ50 nm = ~ 20,000. Considering the square of two gold colloidal size is 6.25 (i.e., (50 nm/20nm)2 = 6.25), γ50 nm /γ20 nm = ~50 is remarkably large and implying that the amount of Aβ1-40 required to complete full aggregation process is not simply described by an individual core gold colloidal size but by a core consisting of a multiple gold colloids. A drastic difference in the slope between two sizes indicate different aggregation processes. A sharper rise may indicate an instantaneous aggregation mechanism, and a moderate rise may be associated with a gradual growth (growing snow-ball).

Nano-size dependent aggregation of Amyloid beta 1-40 peptide-coated gold colloid

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.