. Author manuscript; available in PMC: 2011 Sep 30.

Published in final edited form as: Nature. 2011 Mar 31;471(7340):647–650. doi: 10.1038/nature09918

Table 1.

Effect of labeled lysine and D-ornithine on MtmB pyrrolysyl-peptide ions^a

K isotope^b	D-orn	Observed m/z^c	UAG Residue Formula Assigned^b	m/z error (ppm)^d	UAG-Residue Mass (Da)^e	Residue Identity (mass shift Da)
C₆N₂	−	783.4080²⁺	C₁₂H₁₉N₃O₂	0.77	237.05	O
¹³C₆¹⁵N₂	−	790.9225²⁺	¹³C₁₂H₁₉¹⁵N₃O₂	2.53	252.05	O (+15)
α–^l5N	−	792.4031²⁺^f	C₁₂H₁₉¹⁵N₂NO₂	0.25	239.14	O (+2)
ε-¹⁵N	−	783.9084²⁺	C₁₂H₁₉¹⁵NN₂O₂	1.27	238.16	O (+1)
C₆N₂	+	783.4065²⁺	C₁₂H₁₉N₃O₂	3.06	237.15	O
C₆N₂	+	776.3993²⁺	C₁₁H₁₇N₃O₂	2.19	223.12	O*
¹³C₆¹⁵N₂	+	790.9224²⁺	¹³C₁₂H₁₉¹⁵N₃O₂	0.12	252.19	O (+15)
¹³C₆¹⁵N₂	+	780.4099²⁺	¹³C₆C₅H₁₇¹⁵N₂N₁O₂	0.26	231.16	O* (+8)
C₆N₂^g	+	776.4025²⁺	C₁₁H₁₇N₃O₂	1.93	223.13	O*

₁₉₄AGRPGMGV(O or O*)²⁰²GPETSL₂₀₈ from chymotryptic digestion of MtmB produced in E. coli transformed with pylTSBCD (except where indicated) and mtmB1 supplemented with the listed isotopic form of lysine in the presence and absence of D-ornithine.

Isotopic composition is most abundant natural isotope, unless otherwise indicated.

Accurate mass measured with LTQ-Orbitrap.

Difference between observed and theoretical m/z calculated with indicated elemental formula for UAG-encoded residue.

Average calculated mass (Da) using y- and b-series ions from MS/MS analysis.

M_ox replaces M.

Only pylTSCD present.