TABLE 1.

Selection of peptides for synthesis of isotopically labeled peptide internal standards

Protein	Peptide designation	Sequencea	m/z		Δm	Mascot ion score	εpeptide (M−1 cm−1)
			Observed	Theoretical
Penton	Penton-1412	YSELAPLFDTTR	1,412.717	1,412.706	0.011	79
	Penton-1808	SYNLISNDSTFTQYR	1,808.821	1,808.845	−0.024	91
		pQFTSLTHVFNR	1,332.703	1,332.670	0.033	64
		QFTSLTHVFNR	1,349.717	1,349.700	0.017	77
		SWYLAYNYGDPQTGIR	1,903.990	1,903.900	0.090	70
		RAEAEAAAEAAAPAAQPEVEKPQK	2,433.265	2,433.237	0.028	91
		pQPFQEGFR	991.483	991.463	0.020	48
		QPFQEGFR	1,008.480	1,008.490	−0.010	57
		pQNGVLESDIGVK	1,242.631	1,242.621	0.010	58
		KPVIKPLTEDSK	1,354.860	1,354.794	0.066	38
		TCmmtsPYVYKALGIVSPR	1,712.937	1,712.886	0.051	31
IVa2	IVa2-961	NIFAQAAAR	961.471	961.521	−0.050	46
	IVa2-1633	NFASLQELLSLGGER	1,633.858	1,633.854	0.004	79
		GLPLAISLLLK	1,137.720	1,137.760	−0.040	49
		DMLNEVAPLLR	1,270.690	1,270.682	0.008	48
		RPAALQHQQDQPQAHPGQR	2,163.156	2,163.092	0.064	42
		SAPLHRDPDYADEDPAPVER	2,250.085	2,250.042	0.043	36
Synthetic labeled	AQUA-1422	YSELAPLFDTTR*	1,422.729	1,422.714	0.015	86	23,879
peptides	AQUA-1818	SYNLISNDSTFTQYR*	1,818.831	1,818.853	−0.022	110	29,720
	AQUA-971	NIFAQAAAR*	971.563	971.530	0.033	34	13,137
	AQUA-1643	NFASLQELLSLGGER*	1,643.865	1,643.863	0.002	129	18,980

^apQ, pyro-Glu; DP, acid-sensitive AspPro; R and K, missed cleavages; C_mmts, thiomethylCys; R*, ¹³C₆¹⁵N₄-arginine.