Self-assembly of amyloid beta peptide (Aβ) and alpha-synuclein (a-syn) is an onset step of the fibrillogenesis, which is a hallmark mechanism of Alzheimer’s or Parkinson’s disease. An oligomer formation of Aβ1-40 or a-syn monomers over the nanogold colloidal surface between 10 nm and 100 nm in diameter as an external pH was changed between pH 4 and pH 10. Under pH 4, unfolded monomer was found to construct a dimer or trimer based oligomeric form while a folded monomer avoiding the networking within the rest of the colloidal particles. Remarkably, both Aβand a-syn exhibited specific size/temperature dependence in a reversible self-assembly process. Over 20 nm gold colloid, a reversible assembly process of Aβmonomer was observed in the temperature range of 5 oC and up to 65 oC. While a-syn favored 60 nm gold colloidal surface to conduct a reversible self-assembly below 65 oC. Based on the analysis of the pH value where folded conformation starts, we successfully derived the formula to estimate the covergae ratio of protein over each nanogold colloid. The coverage ratio was found not to possess a linear relationship with the diameter of the gold colloid and ranged between 43 % and 89 %.

Probing protein folding at nano-scale interface

251st National Meeting (2016)

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