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. 2015 Feb 24;290(15):9812–9822. doi: 10.1074/jbc.M114.616219

FIGURE 2.

FIGURE 2.

MS/MS spectra of Pdx1 in vitro and in MIN6 cells. A, tandem mass spectrum of the peptide GQLPFPWMK showing modification of Lys-123 with monomethylation (+14 Da) following treatment with recombinant Set7/9 in vitro. The SEQUEST XCorr for this +2 peptide is 1.83, with a ppm (parts per million) of −1.65. (B) Tandem mass spectrum of the +3 peptide AHAWKGQWAGGAYAAEPEENKR showing monomethylation (+14 Da) of Lys-131 in Pdx1 following treatment with recombinant Set7/9 in vitro. The SEQUEST XCorr for this peptide is 6.19, with a ppm of 0.34. C, representative MS/MS spectrum from an LTQ ion trap for the +2 peptide AHAWKGQWAGGAYAAEPEENKR showing trimethylation at Lys-131 in Pdx1 in transduced MIN6 β cells. The SEQUEST XCorr for this peptide is 2.24, with a ppm of 19.25.