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. 2009 Mar;8(3):467–480. doi: 10.1074/mcp.M800282-MCP200

Fig. 8.

Fig. 8.

LC-MS/MS of tryptic peptides from endogenous MCF-7 ERα. A, spectrum of MH22+ (m/z 710.9) of peptide 288AANLWPpSPLMIK (where pS is phosphoserine). B, spectrum of MH22+ (m/z 670.9) of the analogous unphosphorylated peptide. C, MRM/MS analysis of Ser294 induction following estradiol (E2) treatment showing chromatograms of the y7 Q1/Q3 MRM transitions for the unmodified (670.9/785.5) and phosphorylated (710.9/865.4) peptide from control and estradiol-treated (10 nm; 30 min) cells. D, comparing peak areas for the phosphorylated with unmodified peptides demonstrates that estradiol induces Ser294 oxidation 28-fold. The error bar represents the standard deviation for three biological replicates. XIC, extracted ion chromatogram; cps, counts/s.