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. Author manuscript; available in PMC: 2013 Sep 25.
Published in final edited form as: Biochemistry. 2012 Sep 12;51(38):7488–7495. doi: 10.1021/bi300456f

Figure 5.

Figure 5

LC-MS/MS analysis of the [M + 3]3+ ion (m/z 1067.7) of the CMC-modified peptide (456–483) from Met471Cys TβM. Met471Cys TβM reactions for proteolytic digest and mass spectral analysis were carried out under the following conditions: Met471Cys TβM (15 μM), 50 mM KPi, pH 6 0.1 M KCl, 50 mM ascorbate, 45 μM CuSO4, and 100 μg/mL catalase. The reactions were quenched with 8M urea, reduced with 5 mM TCEP, and capped with 10 mM IAA. Proteolysis was initiated with TPCK trypsin (0.5 μg/mL) and allowed to react overnight at 37 °C. Neat formic acid (1 μL) was added to each reaction before analysis.