The characterization of adsorption of the amyloidogenic peptides, amyloid beta peptide 1-40 (Ab1-40), alpha-synuclein (a syn), and beta-2-microglobulin (b2M) over nano-gold colloidal particle’s surfaces were investigated by using pH dependent UV-Vis absorption spectroscopy. Amyloidogenic peptides generally support unfolded conformations around pH 4 and support folded conformations around pH 10. The peptide affinity of any sizes of gold colloid was confirmed to stably support a layer of peptide. When the peptides were placed over nano gold colloids they were observed to still cause unfolding at pH 4. This leads to a networking of surrounding peptides coated over the nano-gold resulting in a formation of 1 micro meter aggregates. However, there was no clear quantization of the percent of the nano-surface covered by peptide. We established a systematic scheme to extract the surface coverage ratio of peptide by using the pH dependent absorption peak shift. We discovered that critical pH (pHo) and an inverse of the curvature at pHo possessed a linear correlation. Since the larger pHo shift corresponds to the more coverage of peptide, we were able to characterize the surface coverage ratio of peptides for each size of gold colloidal particle. We are currently attempting to rationalize the most appropriate oligomer unit which corresponds to each coverage ratio. This oligomer unit can be associated with the key structure of an intermediate of fibrillogenesis.

Investigation of a nanoscale surface area coverage by a self assembly of amyloidogenic peptides

253rd National Meeting (2017)

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