Western blot analysis of Aβ42 fibrils and prefibrillar oligomers. Aβ42 fibrils (F) and prefibrillar oligomers (O) were run on SDS polyacrylamide gels, transferred to nitrocellulose and probed with 6E10, 4G8, OC and A11 antibodies as indicated at the top of the panel. Both fibrillar and prefibrillar oligomer samples contain bands that react with 4G8 ranging from monomer up to the size of material that accumulates at the top of the gel. OC only stains the bands from fibrillar samples of approximately dimer and above. A11 only stains the prefibrillar oligomer samples. 6E10 does not stain prefibrillar Aβ oligomer samples formed at pH 7.4 as previously reported .