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. Author manuscript; available in PMC: 2015 Feb 15.
Published in final edited form as: Biochem J. 2014 Aug 15;462(1):77–88. doi: 10.1042/BJ20140372

Figure 2. High mass accuracy determination of human tau protein post-translational modifications.

Figure 2

Tau proteins isolated from cognitively normal human brains (Table 1) were digested with trypsin and subjected to LC-MS/MS spectroscopy. (A) MS/MS spectrum and ion assignments for 384AKT*DHGAEIVYK395, where T* corresponds to dehydrobutyrine, a β-elimination product of phospho-Thr. The difference between expected and observed mass for this peptide was −0.00081 Da, corresponding to a mass accuracy of 0.6 ppm. (B) MS/MS spectrum and ion assignment for 306VQIVYK*PVDLSK317, where K* corresponds to dimethyl-Lys. For this methylated peptide, the difference between expected and observed mass was −0.00440 Da, corresponding to a mass accuracy of 2.2 ppm.