Table 1.

Relative abundance ratios of the ¹⁸ O/ ¹⁶ O-labeled glycopeptides and non-glycopeptides in glycoprotein standards

Protein	Peptide sequence	Expected ratio (Sample A:B)	Manually calculated ratio	Self-build quantitative method ratio
Invertase	FATN*TTLTK	1 (1:1)	0.961	0.897
		2 (2:1)	1.997	1.982
		5 (5:1)	4.880	4.856
		0.5 (1:2)	0.563	0.491
		0.2 (1:5)	0.236	0.188
		0.1 (1:10)	0.129	0.104
		10 (10:1)	9.989	9.456
	LMTN*ETSDRPLVHFTPNK	1 (1:1)	0.992	0.953
		2 (2:1)	2.169	1.939
		5 (5:1)	4.980	5.033
		0.5 (1:2)	0.567	0.517
		0.2 (1:5)	0.216	0.192
		0.1 (1:10)	0.103	0.089
		10 (10:1)	10.110	10.050
	ENPYFTNR	1 (1:1)	0.937	0.997
		2 (2:1)	2.040	2.144
		5 (5:1)	5.217	5.462
		0.5 (1:2)	0.474	0.539
		0.2 (1:5)	0.177	0.208
		0.1 (1:10)	0.085	0.111
		10 (10:1)	10.558	11.160
	GLEDPEEYLR	1 (1:1)	0.769	0.837
		2 (2:1)	1.714	1.788
		5 (5:1)	5.014	4.437
		0.5 (1:2)	0.472	0.458
		0.2 (1:5)	0.184	0.183
		0.1 (1:10)	0.084	0.086
		10 (10:1)	9.636	11.110
Fetuin	AESN*GSYLQLVEISR	1 (1:1)	1.138	0.886
		2 (2:1)	1.735	1.588
		5 (5:1)	4.664	5.070
		0.5 (1:2)	0.562	0.424
		0.2 (1:5)	0.219	0.143
		0.1 (1:10)	0.075	0.036
		10 (10:1)	9.849	12.330
	LAPLN*DSR	1 (1:1)	0.980	0.965
		2 (2:1)	1.797	1.824
		5 (5:1)	4.627	4.174
		0.5 (1:2)	0.397	0.415
		0.2 (1:5)	0.158	0.184
		0.1 (1:10)	0.096	0.103
		10 (10:1)	11.289	N a
	ALGGEDVR	1 (1:1)	0.904	0.969
		2 (2:1)	2.116	1.913
		5 (5:1)	5.748	4.589
		0.5 (1:2)	0.469	0.471
		0.2 (1:5)	0.175	0.170
		0.1 (1:10)	0.088	0.080
		10 (10:1)	12.237	11.540
	TPIVGQPSIPGGPVR	1 (1:1)	1.067	1.042
		2 (2:1)	2.102	1.986
		5 (5:1)	5.823	5.559
		0.5 (1:2)	0.460	0.479
		0.2 (1:5)	0.183	0.163
		0.1 (1:10)	0.063	0.100
		10 (10:1)	10.414	10.120

*Denotes the N-glycosylation site.

^a self-build quantitative method did not give a ratio.

Sample A was treated in ¹⁸O water and Sample B in ¹⁶O water. N = self-build quantitative method did not give a ratio.