Table 1.

Quantitative analysis of Src sulfenylation using LC–MS.

Cysteine Residue	Peptide Sequence	Charge	m/z	H:L ratioa	SDb
Cys-185	GAYC(dim)LSVSDFDNAK	2+	814.369	15.48	2.25
	GAYC(dim-d6)LSVSDFDNAK	2+	817.388
Cys-238	HADGLC(dim)HR	2+	523.745	17.36	11.44
	HADGLC(dim-d6)HR	2+	526.764
Cys-245	LTTVC(dim)PTSKPQTQGLAK	3+	637.680	2.25	1.40
	LTTVC(dim-d6)PTSKPQTQGLAK	3+	639.693
Cys-277	LGQGC(dim)FGEVWMGTWNGTTR	2+	1119.509	78.57	5.54
	LGQGC(dim-d6)FGEVWMGTWNGTTR	2+	1122.528
Cys-400	AANILVGENLVC(dim)KVADFGLAR	2+	741.405	13.07	9.84
	AANILVGENLVC(dim-d6)KVADFGLAR	2+	744.424
Cys-483	MPC(dim)PPECPESLHDLMCQCWR c	2+	1342.548	31.39	24.08
	MPC(dim-d6)PPECPESLHDLMCQCWR c	2+	1345.567

All dimedone/dimedone-d6 labeled Src peptides were identified using targeted mass spectrometry analyses. Five out of six dimedone/dimedone-d6 labeled Src peptide pairs were quantified within an average mass error of less than 5 ppm across the peak of elution. XCalibur was used to quantify MPC(dim/dim-d₆)PPECPESLHDLMCQCWR using m/z 1342.548 → [y3]⁺, [y7]⁺, and [y13]⁺ (dim labeled) and m/z 1345.567 → [y3]⁺, [y7]⁺, and [y13]⁺ (dim-d₆ labeled)

^aHeavy to light ratio

^bStandard deviation (n = 3)

^cQuantification of Cys-483 H/L ratio was performed in Xcalibur using three transitions. The three cysteines c-terminal to Cys-483 are carbamidomethylated. All other peptides were quantified by Skyline using four to six transitions from the targeted mass spectrometry experiments with PRM