Aβ-42 protein (AnaSpec, Fremont, CA) and Aβ(14-23) having the sequence HQKLVFFAED (Peptide 2.0 company, VA, USA) were dissolved and sonicated for 5 min in 100 μL of 1,1,1,3,3,3 Hexafluoroisopropanol (HFIP) to destroy pre-aggregated oligomers. Then the solvent was evaporated in vacufuge (1 hr) for complete removal of HFIP. The stock solution of the protein/peptide was prepared in DMSO and kept at −20 °C. Wild-type A140C α-Syn in which the C-terminal alanine was replaced with a cysteine was prepared as described previously36. α-Syn solutions were freshly prepared by dissolving 0.4 to 0.8 mg of the lyophilized powder in 200 μL water (the pH has been adjusted to 11 with NaOH), with the addition of 1 μL of 1 M dithiothreitol (DTT) to break disulfide bonds, followed by the addition of 300 μL of 10 mM sodium phosphate buffer (pH 7.0). The obtained solution was filtered through an Amicon filter with a molecular weight cutoff of 3 kDa at 14,000 rpm for 15 min. The filtration was repeated 3 times to completely remove free DTT. The concentration of the stock solutions was determined by spectrophotometry (Nanodrop® ND-1000, DE) using the molar extinction coefficients 1280 cm−1·M−1 and 120 cm−1·M−1 for tyrosine and cysteine at 280 nm, respectively. In general, freshly prepared stock solutions were used for all the experiments.