. 2016 Mar 7;27(2):61–74. doi: 10.7171/jbt.16-2702-002

TABLE 1.

Extracted Ions for Nt-Dimethylated and -Underivatized GLSDGEWQQVLNVWGK

Amino acid sequence	M_r (calc)	Total measured AUCs
	m/z (Obsrv), elution time	2.5 pmol			0.5 pmol
	m/z (Obsrv), elution time	A1	A2	A3	B1	B2	B3
¹GLSDGEWQQ VLNVWGK¹⁶	1814.895	2.64E + 07	3.75E + 07	2.53E + 07	2.83E + 06	1.67E + 05	3.56E + 06
¹GLSDGEWQQ VLNVWGK¹⁶	908.455 (2+), 57 min	2.64E + 07	3.75E + 07	2.53E + 07	2.83E + 06	1.67E + 05	3.56E + 06
^DimethylGLSDGEWQQ VLNVWGK¹⁶	1842.926	1.03E + 09	1.16E + 09	1.25E + 09	7.06E + 07	1.02E + 07	1.17E + 08
^DimethylGLSDGEWQQ VLNVWGK¹⁶	922.471 (2+), 58 min	1.03E + 09	1.16E + 09	1.25E + 09	7.06E + 07	1.02E + 07	1.17E + 08
^DimethylGLSDGEWQQ VLN_DeamVWGK¹⁶	1843.910	1.18E + 09	1.46E + 09	1.48E + 09	6.44E + 07	7.85E + 06	1.13E + 08
^DimethylGLSDGEWQQ VLN_DeamVWGK¹⁶	922.9681 (2+), 58 min	1.18E + 09	1.46E + 09	1.48E + 09	6.44E + 07	7.85E + 06	1.13E + 08
^DimethylGLSDGEWQ_DeamQ VLN_DeamVWGK¹⁶	1844.895	1.70E + 08	3.18E + 08	3.06E + 08	8.79E + 06	9.27E + 05	1.72E + 07
^DimethylGLSDGEWQ_DeamQ VLN_DeamVWGK¹⁶	923.459 (2+), 59 min	1.70E + 08	3.18E + 08	3.06E + 08	8.79E + 06	9.27E + 05	1.72E + 07

Extracted ion current measurements, expressed as AUC for the myoglobin Nt-dimethylated and -underivatized peptide GLSDGEWQQVLNVWGK. Xcalibur analysis (version 2.1.0) was used to isolate experimental masses (m/z; charge: 2⁺) for the following ions: underivatized, Nt-dimethylated, and Nt-dimethylated peptide with 1 deamidated (Deam) asparagine and with 2 deamidated residues—asparagine and glutamine. For these relative quantitative measurements, MS1 window with mass accuracy of 5 ppm was used. A1, A2, and A3, Gel-bound myoglobin samples, where half of 5 pmol starting material digest was analyzed by LC-MS/MS. B1, B2, and B3, analysis half of 1.0 pmol myoglobin digests. calc, calculated; obsrv, observed.