Figure 1.

Selection of RNA aptamers targeting PFs based on the toxic conformation theory of Aβ42. A, toxic conformation theory of Aβ42. The toxic conformer of Aβ42 forms a turn at Glu-22 and Asp-23, and the E22P mutation enhances the ratio of the toxic Aβ42 conformer. The covalently linked dimer of E22P–Aβ42 has a DAP linker attached at Val-40 in the C-terminal hydrophobic core (E22P–V40DAP–Aβ42 dimer). This dimer produces quasistable PFs (50–100 kDa) after incubation for 48 h at 37 °C (20). B, progression of SELEX monitored by the filter membrane method using real-time PCR. The ratio of bound RNA for each round of selection was plotted as a percentage of total RNA used for the corresponding cycle. The ratios of Aβ to RNA are Aβ:RNA = 400:100 pmol (rounds 1–5), Aβ:RNA = 400:400 pmol (round 6), and Aβ:RNA = 400:800 pmol (round 7). R7, enriched RNA pool after round seven. C, screening of the 36 binding monoclones toward Aβ42 PFs by the filter membrane method using the RiboGreen fluorescent dye. R0, initial RNA pool before selection. D, comparison of the affinity of each clone (E22P–AbD4, –AbD31, and –AbD43) toward PFs and comparison with fibrils produced from WT Aβ42 or E22P–Aβ42. The data are expressed as the means ± S.D. (n = 3). ***, p < 0.001. n.s., not significant.