Table 1. Sequence and M_r of synthetic citrulline-containing peptides, before and after chemical modification.

Synthetic peptide	Sequence	Theor. Mr a	Exp. det. Mr b
Pept1	YAGCitLLTK-NH2	920.5	920.6
Pept2	PIECitTKLY-NH2	1018.6	1018.7
Pept3	PIECitTYLK-NH2	1018.6	1018.7
Modified pept1 c	YAGCit*LLTK-NH2	1158.5	1158.6
Modified pept2 c	PIECit*TKLY-NH2	1256.6	1256.8
Modified pept3 c	PIECit*TYLK-NH2	1256.6	1256.8

^aTheoretical monoisotopic M_r.

^bExperimentally determined M_r.

^cCit* indicates that this citrulline was chemically modified with antipyrine and 2,3-butanedione.