Fig. 4.

Aβ isoforms in extracts from control brain 247 revealed by immunoblotting. A formic acid extract of cerebral cortex from brain C247 was prepared as described in the methods section. A portion of the dried extract was dissolved in PAGE sample buffer and a 15 μl aliquot containing 30 μg of protein (equivalent to 300 μg of tissue) was applied to the lanes developed with R162 and R226. Because mAb 6E10 is much less sensitive than R162 or R226, the formic acid extract was fractionated by size-exclusion as described in the methods section. The fraction containing peptides in the mass range 2,000–12,000 Da was concentrated, and an aliquot containing peptides from 12 mg of tissue was applied to the lane developed with 6E10. The extracts were subjected to PAGE and blotting along with synthetic Aβ standards and molecular mass markers as described in the text. The blots were developed with antibody R162 (to the C-terminus of Aβ_32–40), R226 (to the C-terminus of Abeta_33–42) or mAb 6E10 (to Aβ_4–13). Lane 1 2 fmol Aβ_1–40, lane 2 2 fmol Aβ_17–40, lane 6 150 fmol Aβ_17–40, lane 7 10 fmol Aβ_1–40. Molecular mass markers denoted on the right-hand margin are insulin single chains and aprotinin