Identification of phosphorylation sites using tandem mass spectrometry (MS/MS).

<p>The MS/MS spectra correspond to phosphopeptides with the following mass-to-charge (<i>m/z</i>) ratios, as obtained by trypsin digestion of proteins selected from the 2-DE gel shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130763#pone.0130763.g003" target="_blank">Fig 3</a> (A) <i>m/z</i> 689.810, showing phosphorylation of jacalin-lectin family protein (spot 32) at S195; (B) <i>m/z</i> 1134.612, showing phosphorylation of germin-like protein (spot 31) at T72; (C) <i>m/z</i> 814.872, showing phosphorylation of the Rubisco small subunit (spot 66) at T133; (D) <i>m/z</i> 936.502, showing phosphorylation of ribose 5-phosphate isomerase-related protein (spot 63) at S86. Peaks corresponding to sequential loss of intact amino acid residues from the C or N terminus of the peptide are labeled as b- or y-type ions, respectively.