Figure 1.

Peptide Heterogeneity. Exemplary chosen protein accession 40S ribosomal protein S30 (RS_30) for demonstration of peptide heterogeneity. Every line represents a unique peptide profile (peptide-spectrum-match) identified as originating from the RS_30 protein. iTRAQ ratios are calculated using 116 channel (SJL mouse with standard diet) as reference. For every ratio a box plot giving the lower quartile, median and upper quartile is drawn. Especially for the 117/116 ratio (NZO mouse with high fat diet) the quantitation ratios are very heterogeneous ranging from -0.5 to +1 (corresponding to a 1.4 fold down-regulation or 2 fold up-regulation).