Aβ preparations

Preparing amyloid beta oligomers of different lengths for injections:

1. Dissolve 0.1 mg HFIP treated Aβ42 peptide (JPT Peptide Technologies, Cambridge Bioscience SP-Ab-07_0.1) in 221.5 μl DMSO to obtain a 100 μM solution by vortexing occasionally for 12 min at room temperature.  (Aβ42–1 reverse peptide (Sigma, SCP0048-500UG), which is used as a control, should be prepared the same way.)
2. Sonicate for 5 min.
3. Aliquot the stock solution into individual tubes (5 μl into each tube) and keep at −80°C. 
4. 24 hours before the experiment take 1 μl of the 100 μM stock and dilute by adding 9 μl PBS (Phosphate buffered saline) to yield a 10 μM solution. 
5. Incubate the 10 μM solution either at 4°C, 25°C or 37°C for 24 hr (Kusumoto et al., 1998; Orbán et al., 2010; Whitcomb et al., 2015) depending on which aggregation state is needed. For generating shorter/smaller oligomers use 4°C, for longer oligomers/protofibrils 25°C, and for fibrils use 37°C.
6. After 24 hours, and shortly before injecting, dilute this stock to 10 nM using 1:10 serial dilutions in PBS. This is done by taking 1 μl of the 10 μM aggregated solution and adding 9 μl PBS to make it 1 μM, mixing very gently by tapping on the sides of the tube, then taking 1 μl of the 1 μM solution, adding 9 μl of PBS to have 0.1 μM, mixing very gently, and repeating until the final concentration is 10 nM. 
7. The final 10 nM solution should be injected soon after it is made, as to prevent further potential aggregation of the peptide.