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. Author manuscript; available in PMC: 2012 Sep 1.
Published in final edited form as: Protein Expr Purif. 2011 May 27;79(1):16–24. doi: 10.1016/j.pep.2011.05.012

Figure 5.

Figure 5

Mass spectrometry of the purified peptides for (A) unlabeled Aβ(1–40) and (B) uniformly 13C- and 15N-labeled Aβ(1–40). Theoretical molecular masses for Aβ(1–40) are (A) 4329.8 Da and (B) 4576.8 Da. The error of the mass measurement is ±1 Da. The estimated purity from the mass spectroscopy is more than 90%. The impurity is likely to be Aβ(6–40) as a result of the non-specific cleavage by Factor Xa (see text). The total labeling ratio is ~ 98%.