I 125 – Aβ fragments following APEH cleavage. Soluble Aβ peptide iodinated on amino acid 10 was incubated for 5 hours with or without purified APEH. Following incubation, samples were separated on a 10–20% Tris-tricine gel. The gel was then dried and exposed to film. Full length uncut Aβ fragment, as well as the cleaved Aβ fragments containing the radiolabeled Lys10 are seen on the autoradiograph. Above the autoradiograph is the amino acid sequence of the Aβ peptide. * denotes iodinated amino acid. Arrows indicate APEH cleavage sites.