Mass spectrometry analysis of soluble Aβ
digested by APEH. All three samples were incubated simultaneously for 5 hours at 37°C. A) The ESI-FTICR mass spectrum of Aβ1–40alone. B) The ESI-FTICR mass spectrum of Aβ1–40 incubated with the APEH enzyme. C) The ESI-FTICR mass spectrum of Aβ1–40incubated with both the APEH enzyme and the APEH specific inhibitor Ac-Leu-CK. The m/z regions at 522, 567, and 772 are expanded in the insets and correlate within 3 ppm with the calculated masses for the peptide fragment ions [1–13]3+, [1–14]3+, and [1–19]3+ respectively. D) Observed (Exp.) and calculated (Theo.) masses of the peaks observed in A-C.