Solubility and size distribution of fibrillar Aβ42 oligomers under physiological conditions. A. Aβ42 aggregates were prepared in HFIP-H20 and DMSO-F12 medium as described in Materials and Methods and centrifuged at 100,000 × G for 1 hr. The supernatant and pellet fractions were separated and the pellet resuspended in an equal volume of PBS. Aliquots of the supernatant and pellet were dotted on nitrocellulose and probed with OC antisera. Both the soluble and insoluble fractions contain significant amounts of OC reactive material. B. Aβ42 aggregates formed in DMSO were fractionated by size exclusion chromatography on a Toso-Haas 2000 SWXL column, 1 minute fractions collected and dotted on nitrocellulose and probed with OC antisera. The elution profile detected by UV absorbance is shown in the top panel. The bottom panel shows the OC immunoreactivity which is detected in fractions from 8–14 minutes, indicating that low MW Aβ oligomers are immunoreactive with OC. The arrows indicate the positions of the void volume (Vo), included volume (Vi) and the elution positions of molecular weight standards.