Generation of Aβ42 fractions. Aβ42 peptide was solubilized in 6 M Guanidin-HCl (for sole monomer preparation) or by DMSO, dH2O and Tris (for protofibril preparation) and purified by SEC. (A) single column purification of a sole monomer (M) fraction. Fibrils (F) were derived from monomers by incubation at 37°C, (B) single column purification of a monomer (M) and protofibrils (PF) fraction, (C) purification via two columns connected in series to further separate the protofibrils fraction and obtain large oligomers (LO), medium oligomers (MO) or small oligomers (SO). Left: SEC chromatograms, right: representative TEM images, scale bar corresponds to 200 nm.