Preparation of Aβ solution

Preparation of Aβ solution

Unlabeled lyophilized peptide samples were purchased from Abcam (Cambridge, UK) for the peptides. To obtain monomeric peptide solutions, we dissolved the peptides in high pH solutions as described similarly (65). Briefly, peptides (0.5 mg/ml) were dissolved in a 10% ammonium hydroxide solution. The solution was agitated at room temperature for at least 20 min and distributed in 0.5-ml Eppendorf protein low-bind tubes. Samples were lyophilized and stored at −80°C. For each experiment, one aliquot was dissolved in 60 mM NaOH by shaking at room temperature for 20 min, aiming for a peptide concentration of about 100 μM. The final concentration was determined with absorption spectroscopy (NanoDrop ND 1000 spectrometer) at 280 nm using an absorption coefficient of 1490 M⁻¹ cm⁻¹. Last, PBS buffer [10 mM phosphate buffer, 2.7 mM KCl, and 137 mM NaCl (pH 7.4) from Sigma-Aldrich GmbH, Steinheim Germany] was added to yield a final concentration of 5 μM and obtain a neutral pH value to initiate the aggregation process.

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