Figure 1. Water-soluble (TBS), triton-soluble (TBS-TX) and formic acid-soluble (FA) extracts of human brain contain Aβ immunopositive species with molecular weight consistent for monomer and SDS-stable dimer.

Tissue from 28 brain samples were serially extracted and analysed in duplicate by IP with AW7 and wb with a combination of 2G3 and 21F12, antibodies specific for Aβ terminating at 40 and 42, respectively. Representative western blots of TBS (A), TBS-TX (C) and FA (E) extracts from 7 samples are shown. NS indicates non-specific immunoreactive bands detected when buffer only was IP'd (-ve). Smear denotes immunoreactive material from ~ 9 kDa up to ~ 16 kDa. M refers to monomer and D to dimer. Molecular weight markers are shown on the left. The concentration of monomer or SDS-stable dimer in each sample was determined by comparison with synthetic Aβ standards (5, 10, 20 and 50 ng) and estimated using Li-COR software. The calculated values (B, D and F) are averaged results from 2 different IPs of the same extract analysed on two separate western blots. Monomer is shown in black and dimer in grey.