(A) and (B) represents the alteration in the reduced form (MBP-labeled or hydrolyzed MPB-labeled) and the oxidized form (BIAM-labeled) of peptides identified from H2O2-treated samples, respectively. The MS1 spectrum examples of decreased, unchanged and increased ratio of peptides between the treated and control sample are shown on the right panels in each set. Each circle (open and solid) represents the average ratio of the peptide amount of a certain labeled PTM peptide identified from both the treated and control. Those PTM peptides of statistical significance given by student’s t-test are marked as darker solid circle. The dash lines delineate the cutoffs (± 0.15) of significant alteration (see Experimental Procedures).
Forward and Reciprocal refers to the order of mixing 14N-coded control (C) protein with 15N-coded treated (T) protein and vice versa, respectively. Superscript MPB, MPB[H] and BIAM marks the cysteine residues labeled by MPB, hydrolyzed MPB and BIAM, respectively. M/z represents the ratio of the ion mass to the charge of each PTM peptide.
