Figure 4.

Positional frequency analysis for different PTM sites, see also Figure S3

(A) Phospho [S].

(B) Oxidation [Y].

(C) Quinone [Y].

(D) Dioxidation[Y].

(E) Didehydro[Y].

(F) Methyl [E].

(G) Dehydrated [T].

(H) Dioxidation[M].

(I) Glutathione [C].

(J) Acetyl [Protein N-term]. The positional frequency distribution (%) of a PTM site (dark blue bars) was compared to the distribution of corresponding non-modified amino acid residues (light blue bars) using data from all HLA class I samples grouped by peptide length. p values were derived from the Fisher’s exact test and grouped into different categories as indicated in figure legend.