. Author manuscript; available in PMC: 2013 Apr 6.

Published in final edited form as: J Chromatogr A. 2012 Jan 9;1232:266–275. doi: 10.1016/j.chroma.2011.12.100

Table 1.

Theoretical and observed ratios of stable isotope N-dimethyl labeling and enrichment of tagged nitropeptides (observed ratios were calculated from two independent samples and two analytical replicates for each theoretical ratio and peptide).

Peptides	Ratio (expected 0.33)	Ratio (expected 1.0)	Ratio (expected 3.0)
^#Y^$LQEIYNSNNQK^#	0.34	0.90	3.03
^#EGYY^$GYTGAFR	0.31	0.97	3.11
^#GDY^$DLNAVR	0.25	0.95	3.31
Average ratio	0.30 ± 0.03	0.94 ± 0.02	3.15 ± 0.08

denotes light or heavy N-dimethylation.

denotes 4-Formylbenzoyl (C₈H₅N₁O₂) tag.