Figure 4. Annotated fragment spectra of new identified peptides.

Four MS/MS spectra are shown exemplarily of the new identified DN biomarkers, like collagen alpha-1 (I) fragments (A, C), alpha-1-antitrypsin fragment (B), and a collagen alpha-2 (I) fragment (D). The corresponding sequence is displayed above each spectrum (p = hydroxylation of P; k = hydroxylation of K; m = oxidation of M). Identified b-ions are marked in blue and y-ions in red color.