The Effect of Ultrasonication on the Fibrillar/ Oligomeric Structures of Aβ1−42 at Different Concentrations

Abstract

The number of disease states linked the aberrant regular protein conformations to oligomers and amyloid fibrils. Amyloid beta 1–42 (Aβ₁₋₄₂) peptide is very hydrophobic and quickly forms the β-rich structure and fibrillar protein aggregates in some solutions and buffer conditions. Ultrasonication pulses can disrupt amyloid fibrils to smaller fragments and produce Aβ₁₋₄₂ peptides of different sizes and oligomers. Herein, we investigated the effects of buffer and ultrasonication on Aβ₁₋₄₂ structure at low and high concentrations. After ultrasonication, the Western blot results showed that Aβ₁₋₄₂ fibrils were disaggregated into different sizes. The transmission electron microscopy results indicated Aβ₁₋₄₂ at low concentration (25 µM) in Ham’s/F12 phenol red-free culture medium formed short-size fragments and oligomers. In comparison, Aβ₁₋₄₂ at higher concentration (100 µM) formed fibrils that break down into smaller fragments after ultrasonication. However, after regrowth, it formed mature fibrils again. Cell viability assay indicated that Aβ₁₋₄₂ oligomers formed at a low concentration (25 µM) were more toxic to PC12 cells than other forms. In conclusion, by applying ultrasonication pulses and controlling peptide concentration and buffer condition, we can rich Aβ₁₋₄₂ aggregates with a particular size and molecular structure.