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. Author manuscript; available in PMC: 2020 Aug 30.
Published in final edited form as: J Am Soc Mass Spectrom. 2008 Mar 4;19(5):729–740. doi: 10.1016/j.jasms.2008.02.008

Figure 5.

Figure 5.

vMALDI-MS/MS, MS3 and MS4 identification of phosphorylated tryptic peptide EAGPPAFYRPNpS154DNRR (residues 143–158) from MCF-7 cells treated with E2. (a) The precursor ion [M + H]+ at m/z 1927.0 selected for MS/MS analysis. −P represents loss of phosphoric acid, i.e., loss of 98 Da. (b) MS3 spectrum of m/z 1829.0 [M+H−98]+ confirming that Ser-154 is now dehydro-alanine. The c11 fragment ion (1217.7 m/z) was fragmented (MS4; for additional sequence information see inset). (c) MS/MS of the unmodified peptide at m/z 1847.0 corresponding to EAGPPAFYRPNSDNRR. The c11 ion (1217.7 m/z) was further fragmented (MS3; see inset).