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. Author manuscript; available in PMC: 2021 Dec 15.
Published in final edited form as: Anal Chem. 2020 Nov 24;92(24):15693–15698. doi: 10.1021/acs.analchem.0c03104

Figure 3. Identification of PTMs in the ECM proteins.

Figure 3.

Representative MS/MS spectra of identified ECM PTMs. Precursor ions are annotated with green stars. a. Precursor ion Collagen alpha-2 (I) chain peptide with proline (P) hydroxylation (+ 16 Da). [(M+2H)2+, 788.9 m/z, Expt’l: 1,575.8 Da, 0.8 ppm]. b. Fibrillin-1 peptide modified with cysteine (C) carbamidomethylation (+ 57 Da) and asparagine (N) hydroxylation (+16 Da). Precursor ion [(M+3H)3+, 1102.4 m/z, Expt’l: 3,304.3 Da, 1.4 ppm]. c. Host cell-factor-1 with (N)-linked acetylhexosamine (HexNAc) glycosylation (+203 Da). Precursor ion [(M+3H)3+, 802.1 m/z, Expt’l: 2,403.3 Da, 0.6 ppm]. HCFC1 co-eluted with a highly abundant peptide identified as splicing factor 3b subunit 2, where corresponding b and y ions are denoted with gray circles. d. Serpin B6 with N-terminal acetylation (+42 Da). Precursor ion [(M+2H)2+, 959.0 m/z, Expt’l: 1,916.0 Da, 0.2 ppm].