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. Author manuscript; available in PMC: 2009 Jul 1.
Published in final edited form as: Chem Res Toxicol. 2008 Jun 12;21(7):1432–1442. doi: 10.1021/tx800093k

Figure 3.

Figure 3

Effects of signal-to-noise (S/N) ratio on ability to observe d0/d5 isotopic signatures in MALDI-TOF mass spectra of tryptic digests of liver cytosolic proteins from rats treated with deuterated thiobenzamide (d0/d5 = 1:1). A) S/N ≥ 10. The spectrum shows the benzimidoyl-modified peptide 204GVFTK*ELPSGK214 from the digest of spot 56 (peroxiredoxin 6). B) S/N ∼ 4−5. The spectrum shows the benzoyl-modified peptide 81AVVK*M(O)EGDNK90 from the digest of spot 12 (LFABP). C) S/N < 3. The spectrum shows the benzimidoyl-modified peptide 40LK*ETEYNVR48 from the digest of spot 100 (arginase). D) S/N < 3. The spectrum shows three different benzoyl-modified peptides in a single digest of spot 12 (LFABP): 34DIK*GVSEIVHEGK46 at m/z 1514.78, 21AM(O)GLPEDLIQK*GK33 at m/z 1519.77, and 85M(O)EGDNK*M(O)VTTFK96 at m/z 1536.70 (where * indicates the modified lysine).