Figure 4.

Mass spectrum of Aβ derived from A4CT-V44F and A4CT-wt. By using antibody 4G8, Aβ was first immunoprecipitated from the conditioned medium of COS7 cells expressing SPA4CT-wt or V44F and then analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition to the measured molecular masses, peaks in the spectrum were labeled with Aβ peptide sequence numbers. The main peaks are labeled with arrows. The peptides start at the N terminus with the two additional amino acids leucine and glutamic acid (Fig. 1).