Figure 2From: Blind search for post-translational modifications and amino acid substitutions using peptide mass fingerprints from two proteasesScreenshot of the MassShiftFinder main window. The data are taken from an experiment on guanidinated enolase (see additional file 2: ExperimentalExamples.pdf). The mass shift boundaries are set to restrict the detected mass shift mainly to guanidinations (mass shift of 42 Da). The highlighted row (14) indicates an "X-Z" mass shift (see Figure 1). Rows 11–13 show a mass shift occurring in the Y-area, with one tryptic peptide (1316.7) paring up with three chymotryptic peptides. The right-most column (UniMod hits) for most of the rows indicates that there are three modifications (acetylation, tri-methylation and guanidination) that are consistent with a mass shift of 42 for the indicated peptides. Row 16 has 0 UniMod hits because the calculated mass shift is more than 0.1 Da from the three mentioned modifications; furthermore, this mass shift cannot be due to guanidinated K as only one of the peptides contains a K.Back to article page